(a)[1]
Find the bearing from $B$ to $A$.
(b)[4]
Calculate the length of $BC$.
(c)[5]
Boat $B$ departs from port $B$ at $10.00\,\text{am}$ and travels directly to port $A$ at an average speed of $48\,\text{km h}^{-1}$. Boat $C$ sets off from port $C$ at $10.15\,\text{am}$, heads straight to port $A$, and gets there $7$ minutes before boat $B$. Find the average speed of boat $C$ in $\text{km h}^{-1}$.