A Source contains two phosphors radio nuclides $_{15}P^{32}(T_{1/2}=14.3\;days)$ and $_{15}P^{33} (T_{1/2} =25.3\;day)$ Initially $10\%$ of the decays come from $_{15}P^{33}$. How long one must wait until $90\%$ do so ?

Question

$\begin{array}{1 1} 20.85\;days \\ 2.085\;days \\ 208.5\;days \\ 2.085\;days \end{array}$