number of strikes in the allotted time is thus
\begin{equation}
\Delta N = \deriv{t}{N} \cdot \Delta t = \frac{I\Delta t}{q}
- = \ans{17.9\E{15}\U{protons} = 17.9\U{petaprotons}} \;.
+ = \ans{18.0\E{15}\U{protons} = 18.0\U{petaprotons}} \;.
\end{equation}
\end{solution}