TASK DEFINITION: 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: Problem: in what time will a train 120 m long cross an electric pole, it its speed be 121 km / hr ?
Options: a. 2.5, b. 2.7, c. 2.9, d. 3.6, e. 2.1

SOLUTION: d

PROBLEM: Problem: a bag has 9 green balls and 23 pink balls. how many green balls should be added to the bag so that the ratio of green balls and pink balls in the bag becomes 1: 1 ?
Options: a. 10, b. 11, c. 12, d. 13, e. 14

SOLUTION: e

PROBLEM: Problem: in one day, juan sends keith 8 times as many messages as he sends laurence, and laurence sends missy 4.5 times as many messages as he receives from juan. if missy received 18 messages from laurence, how many messages does keith receive from juan ?
Options: a. 13, b. 26, c. 32, d. 48, e. 56

SOLUTION:
c