I think it will be 140cm3 because you would do 7x20 to get your answer
The question is asking we convert from (x, y) coordinate to (r, theta) coordinates.
So (0, 4) to (r, theta)
x = 0 and y = 4.
r = âš (x^2 + y^2)
r = âš (0^2 + 4^2)
r = âš (0 + 16)
r = 4
Also theta = tan^(-1)(x/y) = tan^(-1) (0/4) = 0
So theta = 0
Hence the (r, theta) coordinate is (4, 0)