For which of the following increasing functions f does (f inverse)′(20)=1/5

A)
f(x)=x+5
f of x, equals, x plus 5
B)
f(x)=x3+5x+20
f of x, equals, x cubed, plus 5 x, plus 20
C)
f(x)=x5+5x+14
x to the fifth power, plus 5 x, plus 14
D)
f(x)=ex+5x+19
e to the x power, plus 5 x, plus 19