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: 10 ^ ( 600 ) ã · 10 ^ ( 580 ) = ?
Options: a. 10 ^ 10, b. 10 ^ 20, c. 10 ^ 22, d. 10 ^ 23, e. 10 ^ 24
b

Problem: a train which has 430 m long, is running 45 kmph. in what time will it cross a person moving at 9 kmph in same direction ?
Options: a. 56 sec, b. 43 sec, c. 36 sec, d. 29 sec., e. 19 sec.
b

Problem: the average of all odd numbers up to 200 is
Options: a. 50, b. 100, c. 120, d. 75, e. 80

b