Answer
$R = 8.88 \times 10^{10} s^{-1}$
Work Step by Step
The decay rate equals to the production rate. The equation of decay rate is $R = \lambda N$, Given the activity of the $^{56}Mn$ produced in the target reaches a final value of $8.88 \times 10^{10} Bq$.
This means $R = \lambda N = 8.88 \times 10^{10} s^{-1}$ (because the production rate = decay rate)
