Find the value of wave number $(\bar{v})$ in terms of Rydberg's constant, when transition of electron takes place between two levels of $\mathrm{He}^{+}$ ion whose sum is 4 and difference is $2 .$
(a) $\frac{8 R}{9}$
(b) $\frac{32 R}{9}$
(c) $\frac{3 R}{4}$
(d) none of these