Given the task definition and input, reply with output. 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: the average height of 20 students in a class was calculated as 175 cm. it has later found that the height of one of the students in the class was incorrectly written as 151 cm whereas the actual height was 136 cm. what was the actual average height of the students in the class ?
Options: a. 174.75 cm, b. 174.25 cm, c. 173.75 cm, d. 173.25 cm, e. 172.75 cm
b