\begin{problem*}{27.1}
-A proton beam in an accelerator carries a current of $125\U{$\mu$A}$
+A proton beam in an accelerator carries a current of $125\U{$\mu$A}$.
If the beam is incident on a target, how many protons strike the
target in a period of $23.0\U{s}$.
\end{problem*}