Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.

[EX Q]: Problem: a student travels from his house to school at 12 km / hr and reaches school 2 hours late. the next day he travels 20 km / hr and reaches school 1 hour early. what is the distance between his house and the school ?
Options: a. 90, b. 100, c. 110, d. 120, e. 130
[EX A]: a

[EX Q]: Problem: there are 27 different 3 - digit integers that can be formed using only the digits 3, 4 and 5. if all 27 of the integers were listed, what would their sum be ?
Options: a. 11,888, b. 11,988, c. 12,088, d. 12,188, e. 12,288
[EX A]: b

[EX Q]: Problem: in a school with 632 students, the average age of the boys is 12 years and that of the girls is 11 years. if the average age of the school is 11 years 9 months, then the number of girls in the school is
Options: a. 150, b. 200, c. 250, d. 158, e. none
[EX A]:
d