Provide your best answer for the following math problem. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The problem is: a circular path of 12 m radius has marginal walk 2 m wide all round it . find the cost of leveling the walk at 50 p per m 2 ?
rs . 81.72
158.5 m²