You do this problem by making use of the formula for the surface area of a sphere. It expresses the area in terms of the radius. Fill in the given information and solve for the radius.
... A = 4π·r²
... 2.94·10⁹ = 4π·r²
... (29.4·10⁸0/(4π) = r² ≈ 2.34·10⁸ . . . . . now take the square root to find r
... r ≈ 1.53·10⁴ = 15,300 . . . miles
The appropriate choice is ...
... (B) 15,300
