What volume at NTP of ammonia gas will be required to be passed into 30ml of $NH_2SO_4$ solution to bring down the acid normality to 0.2N

Question

$\begin{array}{1 1}(a)\;537.6ml\qquad(b)\;436ml\qquad(c)\;500ml\qquad(d)\;493.1ml\end{array}$