$pH$ of the solution containing 50.0 mL of 0.3 M HCl and 50.0 mL of 0.4 M $NH_3$ is

Question

[Given $pK_a (NH^+_4)$ = 9.26]

 

(a) 4.74

(b) 9.26

(c) 8.78

(d) 4.63