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.

Q: Problem: a train 510 m long is running at a speed of 45 km / hr. in what time will it pass a bridge 140 m long ?
Options: a. 40, b. 52, c. 26, d. 21, e. 14

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

A: b
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Q: Problem: car a is 16 miles behind car b, which is traveling in the same direction along the same route as car a. car a is traveling at a constant speed of 58 miles per hour and car bis traveling at a constant speed of 50 miles per hour. how many hours will it take for car a to overtake and drive 8 miles ahead of car b ?
Options: a. 1.5, b. 2.0, c. 2.5, d. 3.0, e. 3.5

A:
d
****