Answer
$9.5\times10^{-4}V$.
Work Step by Step
$$|\epsilon_{av}|=N|\frac{\Delta \Phi}{\Delta t}|$$
$$=NA|\frac{B_f-B_i}{\Delta t}|=\frac{NA\mu_0nI}{\Delta t}$$
$$\epsilon_{av}=\frac{(12)(8.00\times10^{-4}m^2)\mu_0(9000m^{-1})(0.350A)}{0.0400s}$$
$$=9.5\times10^{-4}V $$
