Solution:
Solution:
Half life of $$A = \ell n^2$$
$$t_{1/2} = \frac{\ell n2}{\lambda}$$
$$\lambda_A = 1$$
at $$t = 0 \; R_A = R_B$$
$$N_A e^{- \lambda AT} = N_B e^{-\lambda BT}$$
$$N_A = N_B $$ at $$t = 0$$
at $$t = t \; \frac{R_B}{R_A} = \frac{N_0 e^{\lambda_Bt}}{N_0 e^{- \lambda_A t}}$$
$$e^{-(\lambda_B - \lambda_A)t} = e^{-t}$$
$$\lambda_B - \lambda_A = 3$$
$$\lambda_B = 3 + \lambda_A = 4$$
$$t_{1/2} = \frac{\ell n2}{\lambda_B} = \frac{\ell n 2}{4}$$
