If $ f(x+y)=f(x).f(y)$ for all x and y and if $f(5)=2$ and $f'(0) =3$ find $f'(5)$

Question

$\begin{array}{1 1}(A)\;2 \\(B)\;6 \\(C)\;7 \\(D)\;none\;of\;these \end{array}$