d
\({\text{R}} = \lambda {\text{N}} = \frac{{{\text{ln2}}}}{{{{\text{t}}_{{\text{1/2}}}}}}\left( {\frac{M}{{{M_0}}} \times {N_A}} \right)\)

\(R = \frac{{0.693}}{{1620g}}\left( {\frac{{1g}}{{226\frac{g}{{mol}}}} \times 6 \times {{10}^{23}}} \right)\)

\( = \frac{{0.693 \times 6 \times {{10}^{23}}}}{{1620 \times 365 \times 24 \times 3600 \times 226}} = 3.61 \times {10^{10}}dps\)