Detailed Instructions: 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 circular ground whose diameter is 70 metres, has a 2.8 metre - broad garden around it. what is the area of the garden in square metres ?
Options: a. 540.72, b. 740.64, c. 640.64, d. 620.45, e. 725.26
A:
c