Highest_Cost_Scenario_Identification

Highest Cost Scenario Identification

This skill covers two question types in the dabstep dataset, both requiring fee calculation from fees.json.

Fee Formula

fee = fixed_amount + rate * transaction_value / 10000

In fees.json: an empty list [] for aci or merchant_category_code means the rule does NOT apply to any specific value of that field — skip it when iterating. A null value on other fields (e.g. is_credit, card_scheme) means the rule applies to ALL values of that field.

Data facts (verified from the actual files):

• fees.json has 1000 rules; card_scheme is never null; aci is either [] or a list of letters (never null)
• is_credit: True = credit only, False = debit only, null/None = both
• ACI values present: A, B, C, D, E, F only (G does not appear in any fee rule)
• Card schemes: GlobalCard, NexPay, TransactPlus, SwiftCharge

Question Type 1: Most Expensive MCC

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

Algorithm:

1. Load fees.json
2. For every rule, skip if merchant_category_code is empty ([])
3. Compute fee = fixed_amount + rate * X / 10000
4. For each MCC in the rule's list, track the maximum fee seen across all rules
5. Return all MCCs (sorted ascending) that tie for the global maximum fee

Critical: No card_scheme or is_credit filter for "in general" MCC questions. Include ALL MCCs from fees.json — do NOT restrict to MCCs listed in merchant_category_codes.csv.

Output format: Comma-separated MCC integers, sorted ascending. Example: 3000, 3001, 7512

import json

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

transaction_value = X  # from question
mcc_max_fees = {}

for rule in fees:
    mcc_list = rule['merchant_category_code']
    if not mcc_list:  # skip [] (no MCC applies)
        continue
    fee = rule['fixed_amount'] + rule['rate'] * transaction_value / 10000
    for mcc in mcc_list:
        if mcc not in mcc_max_fees or fee > mcc_max_fees[mcc]:
            mcc_max_fees[mcc] = fee

max_fee = max(mcc_max_fees.values())
result = sorted([mcc for mcc, f in mcc_max_fees.items() if f == max_fee])
print(', '.join(str(m) for m in result))

Question Type 2: Most Expensive ACI

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

Algorithm:

1. Load fees.json
2. Filter rules: card_scheme == CardScheme AND is_credit is True or None
3. Skip rules where aci list is empty ([])
4. Compute fee = fixed_amount + rate * X / 10000
5. For each ACI in the rule's list, track the maximum fee seen
6. Return the ACI with the highest fee; if tied, return the alphabetically lowest

Output format: A Python list containing one letter string. Example: ['E']

CRITICAL — do NOT return the fee amount as the answer. The task instructions show e.g., <answer>0.23</answer> as a generic format placeholder — that 0.23 is irrelevant to ACI questions. Your answer must be the ACI letter (['A'], ['B'], ... ['F']), never a numeric fee value.

import json

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

card_scheme = 'NexPay'      # from question
transaction_value = 1       # from question
aci_max_fees = {}

for rule in fees:
    if rule['card_scheme'] != card_scheme:
        continue
    # None means applies to all (credit and debit); include for credit transactions
    if rule['is_credit'] is not None and rule['is_credit'] != True:
        continue
    aci_list = rule['aci']
    if not aci_list:  # skip [] (no ACI applies)
        continue
    fee = rule['fixed_amount'] + rule['rate'] * transaction_value / 10000
    for aci in aci_list:
        if aci not in aci_max_fees or fee > aci_max_fees[aci]:
            aci_max_fees[aci] = fee

max_fee = max(aci_max_fees.values())
winners = sorted([aci for aci, f in aci_max_fees.items() if f == max_fee])
answer = winners[0]  # lowest alphabetical in case of tie
print([answer])      # output as a list, e.g. ['E']

Common Mistakes

1. MCC filtering: Never exclude an MCC just because it's absent from merchant_category_codes.csv. The fee rules are the sole source of truth.
2. ACI answer is a letter, not a fee: Return the ACI letter in a list (e.g., ['E']). The 0.23 seen in the task instructions is only a generic format example — it has no connection to the correct ACI answer.
3. Empty lists []: Skip rules where merchant_category_code or aci is []; these rules don't apply to any specific MCC or ACI.
4. is_credit for ACI questions: Include rules with is_credit=None (applies to all transaction types), not only is_credit=True.
5. Tie-breaking for ACI: When multiple ACIs share the maximum fee, return the alphabetically first one (e.g., 'A' before 'B').