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.

Problem: a cyclist bikes x distance at 8 miles per hour and returns over the same path at 10 miles per hour. what is the cyclist ' s average rate for the round trip in miles per hour ?
Options: a. 8.1, b. 8.9, c. 8.6, d. 8.3, e. 9.0
b

Problem: what least number should be added to 1057, so that the sum is completely divisible by 23
Options: a. a. 4, b. b. 1, c. c. 2, d. d. 3, e. e. 5
b

Problem: a card board of size 34 * 14 has to be attached to a wooden box and a total of 35 pins are to be used on the each side of the card box. find the total number of pins used.
Options: a. 135, b. 136, c. 137, d. 138, e. 139

b