Answer
The deuterons strike the block at a rate of $~~9.4\times 10^{13}~deuterons/s$
Work Step by Step
A deuteron is a particle consisting of a proton and a neutron. This it has a charge of $e$
We can find the rate at which the deuterons strike the block:
$\frac{15\times 10^{-6}~A}{1.6\times 10^{-19}~C/deuteron} = 9.4\times 10^{13}~deuterons/s$
The deuterons strike the block at a rate of $~~9.4\times 10^{13}~deuterons/s$
