(a(i))[1]
Write down the mathematical term for line $PQ$.
(a(ii))[1]
Explain why angle $OPB$ equals $90^{\circ}$.
(a(iii))[3]
Find the value of $x$.
(b(i))[2]
Find the value of $a$. Give a reason for your answer.
(b(ii))[2]
Find the value of $b$. Give a reason for your answer.
(b(iii))[2]
Find the value of $c$.
(c)[3]
Calculate the value of $x$.