Task: Question Answering
Input (English): Problem: tourist purchased a total of 30 travelers checks in $ 50 and $ 100 denominations. the total worth of the travelers checks is $ 1800. how many checks of $ 50 denominations can he spend so that average amount ( arithmetic mean ) of the remaining travelers checks is $ 100 ?
Options: a. 4, b. 12, c. 15, d. 20, e. 24
Output (English): e