Q: 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 traveled for two days. on the second day the cyclist traveled 4 hours longer and at an average speed 10 mile per hour slower than she traveled on the first day. if during the two days she traveled a total of 210 miles and spent a total of 12 hours traveling, what was her average speed on the second day ?
Options: a. 5 mph, b. 10 mph, c. 20 mph, d. 30 mph, e. 40 mph
A:
d