I suspect 4/2 should actually be 4/3, since 4/2 = 2, while 4/3 would make V the volume of a sphere with radius r. But I'll stick with what's given:
In Mathematica, you can check this result via
D[4/2*Pi*r^3, r]
Answer:
just apply the formulas then see dummy
Prime factorization of 525 is 3×5×5×7