witch function defines (g . f)(x)
f(x)=log(5x)
g(x)=5x+4
a.) (g . f) (x)=5x log(5x) + 4log(5x)
b.) (g . f) (x)=5x log(5x)+ 4
c.) (g . f) (x)=5x + 4 +log(5x)
d.) (g . f) (x)=5x - 4 - log(5x)
