(a)[1]
Find $\overrightarrow{OB}$, giving your answer in terms of $a$ and $c$.
(b(i))[1]
Express, in terms of $a$ and $c$ and in its simplest form, $\overrightarrow{AM}$.
(b(ii))[2]
Express, in terms of $a$ and $c$ and as simply as possible, $\overrightarrow{AT}$.
(c)[2]
Show that $ATM$ lies on a straight line.