Prize regions on a circular target

A target of radius 15 cm contains non-overlapping prize circles: A of radius 3 cm lies inside C of radius 7 cm, and B has radius 4 cm. The first prize is the part of C outside A, second prize is A, third prize is B, and the remaining shaded board wins nothing. Assuming a uniform hit on the board, find the probability of

1. winning either of the top two prizes,
2. winning first prize,
3. winning nothing. Based only on whether a prize is more likely than no prize, should a player enter?