Ans: C
Total words she typed in the first $3$ hours
Total words she typed in the first $3$ hours
$\begin{array}{cl}
= & 3 \times 60 \times 63 \\
= & 11~340 \mbox{ words}
\end{array}$
Total words she typed in the last $4$ hours
$\begin{array}{cl}
= & 4 \times 60 \times 56 \\
= & 13~440 \mbox{ words}
\end{array}$
Therefore the average typing speed for the $7$ hours
$\begin{array}{cl}
= & \dfrac{11~340+13~440}{7\times 60} \\
= & 59 \mbox{ words per minute}
\end{array}$
