Let  $g:R\to R$ be given by  $g\left(x\right)=3+4x$. If  $g^n\left(x\right)=\left(gogo\mathrm{....}og\right)\left(x\right)$ , ( $g$ repeated n times) and  $g^n\left(x\right)=A+Bx$ then A and B are