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 10 km / hr and reaches school 2 hours late. the next day he travels 18 km / hr and reaches school 1 hour early. what is the distance between his house and the school ?
Options: a. 65.0, b. 67.5, c. 70.0, d. 72.5, e. 75.0
[EX A]: b

[EX Q]: Problem: how many positive even integers less than 100 contain digits 5 or 7 ?
Options: a. 10, b. 17, c. 18, d. 19, e. 20
[EX A]: a

[EX Q]: Problem: arun purchased 30 kg of wheat at the rate of rs. 11.50 per kg and 20 kg of wheat at the rate of 14.25 per kg. he mixed the two and sold the mixture. approximately what price per kg should be sell the mixture to make 15 % profit ?
Options: a. 14.49, b. 16.33, c. 16.35, d. 16.3, e. 16.32
[EX A]:
a