Highest_Cost_Scenario_Identification

Highest Cost Scenario Identification

This skill covers two question patterns in the dabstep dataset, both requiring you to find the scenario that maximizes the payment processing fee.

Fee Formula

From manual.md:

fee = fixed_amount + rate * transaction_value / 10000

All fee rules are in fees.json. Key rule fields:

• card_scheme: card network name (e.g. "GlobalCard", "NexPay", "TransactPlus", "SwiftCharge")
• is_credit: true (credit only), false (debit only), null (applies to both)
• aci: list of ACI letters this rule covers; null means all ACIs; empty list [] means no ACI matches (rule is ACI-agnostic/not ACI-specific — treat as applying to all ACIs when empty)
• merchant_category_code: list of integer MCC codes this rule covers
• fixed_amount, rate: fee components

Critical null semantics: null in any field = applies to all values of that field.

Question Type 1: Most Expensive MCC

Pattern: "What is the most expensive MCC for a transaction of X euros, in general?"

Algorithm

import json

with open('fees.json') as f:
    fees = json.load(f)

transaction_value = X  # euros, from the question

mcc_max_fee = {}  # mcc_code -> max fee seen

for rule in fees:
    fee = rule['fixed_amount'] + rule['rate'] * transaction_value / 10000
    for mcc in rule['merchant_category_code']:
        if mcc not in mcc_max_fee or fee > mcc_max_fee[mcc]:
            mcc_max_fee[mcc] = fee

overall_max = max(mcc_max_fee.values())
result_mccs = sorted([mcc for mcc, f in mcc_max_fee.items() if f == overall_max])
print(', '.join(str(m) for m in result_mccs))

Critical Rules

• Do NOT filter MCCs by merchant_category_codes.csv. Use all MCCs that appear in fees.json rules. The fees.json is the authoritative source for which MCCs have fee rules.
• "In general" means: find the maximum possible fee over ALL rules, with no restriction on card_scheme, is_credit, aci, account_type, capture_delay, etc.
• If multiple MCCs tie at the maximum fee, list all of them sorted numerically.

Common Error to Avoid

Wrong: Filtering MCCs to only those in merchant_category_codes.csv (this incorrectly excludes valid MCCs like 3003, 7231 that appear in fees.json but not in the MCC reference file).

Question Type 2: Most Expensive ACI for a Specific Card Scheme

Pattern: "For a credit transaction of X euros on [CardScheme], what would be the most expensive ACI? In the case of a draw, return the ACI with the lowest alphabetical order."

Algorithm

import json

with open('fees.json') as f:
    fees = json.load(f)

card_scheme = "GlobalCard"   # from the question
transaction_value = 1.0       # euros, from the question
ALL_ACIS = ['A', 'B', 'C', 'D', 'E', 'F', 'G']

aci_max_fee = {}  # aci -> max fee

for rule in fees:
    # Filter by card scheme
    if rule['card_scheme'] != card_scheme:
        continue
    # Filter by credit: keep if is_credit is True or None (null = applies to both)
    if rule['is_credit'] == False:
        continue

    fee = rule['fixed_amount'] + rule['rate'] * transaction_value / 10000

    # Determine which ACIs this rule covers
    rule_acis = rule['aci']
    if rule_acis is None:
        rule_acis = ALL_ACIS       # null = all ACIs
    elif len(rule_acis) == 0:
        rule_acis = ALL_ACIS       # empty list = applies to all ACIs (no ACI restriction)

    for aci in rule_acis:
        if aci not in aci_max_fee or fee > aci_max_fee[aci]:
            aci_max_fee[aci] = fee

# Find the ACI(s) with the highest fee
if not aci_max_fee:
    print("Not Applicable")
else:
    max_fee = max(aci_max_fee.values())
    best_acis = sorted([a for a, f in aci_max_fee.items() if f == max_fee])
    # Tiebreak: alphabetically lowest
    answer = best_acis[0]
    print(f"['{answer}']")

Critical Rules

• Filter is_credit: For "credit transaction" questions, keep rules where is_credit is True or is_credit is None. Exclude rules where is_credit == False.
• ACI null vs empty list: Both null and [] in the aci field mean the rule applies to all ACIs. Do NOT skip rules with empty aci lists.
• Output format: The answer is the ACI letter (e.g. C, E), NOT the fee value. Return in list format: ['C'].
• Tiebreak: If multiple ACIs share the maximum fee, return the one that comes first alphabetically.

Common Errors to Avoid

1. Outputting the fee amount (e.g. "0.23") instead of the ACI letter — the question asks WHICH ACI, not what the fee is.
2. Treating empty aci list as "no ACIs" — empty list means all ACIs apply (same as null).
3. Forgetting null is_credit rules — rules with is_credit: null apply to credit transactions too.

Output Format

• MCC questions: comma-separated list of integer MCC codes, sorted numerically. E.g.: 3000, 3001, 3002, 3003, 7011, 7032, 7512, 7513
• ACI questions: single letter in a list. E.g.: ['C']
• If no applicable rules exist: Not Applicable

Validation Checklist

Before finalizing your answer:

1. Did you use the correct fee formula: fixed_amount + rate * transaction_value / 10000?
2. For MCC questions: did you search ALL fee rules without filtering by card scheme or credit type?
3. For ACI questions: did you filter by the correct card scheme AND include is_credit=null rules?
4. Is your output the MCC codes / ACI letters (not the fee amount)?
5. Are ties handled correctly (all MCCs listed / alphabetically first ACI)?