If f(x)=5x^3 and g(x)=x+1, find (f•g)(x)

Hello from MrBillDoesMath!
Answer:
5 x^3 + 15 x^2 + 15 x + 5 , none of the provided choices
Discussion:
f(x) = 5 x^3
g(x) = x+ 1
=>
(f•g)(x) =
f(g(x)) =
f(x+1) =
5 * (x+1)^3 =
5 x^3 + 15 x^2 + 15 x + 5
which is none of the provided answers.
Thank you,
MrB