A solid is defined by a surface:

x^2 + y^2 + z^2 ≤ b^2

Whereby, 0 ≤ x, 0 ≤ y, 0≤ z

The density varies in proportion to the distance from the centre.

Hence deduce the mass of the solid.

I assume i use sphereical polar coordinates, but not entirely sure where i go beyond that.

Any help is appreciated!