Answer
$f(4)-f(3)$ = $0.125$
$f(4)$ = $12.125$
Work Step by Step
$f'(x)$ = $\frac{f(x+h)-f(x)}{h}$
assume x = 3, h =1
$f'(3)$ = $\frac{f(3+1)-f(3)}{1}$
$x^{-3}$ = $f(4)-f(3)$
$f(4)-f(3)$ = $0.125$
${f(4)-12}$ = $0.125$
$f(4)$ = $12.125$