Circle $P$ has diameter $CD$. Point $B$ is on the circle such that $m\angle BPC=30$ degrees. Point $A$ is on the circle such that $AD$ is parallel to $PB$.
What is the degree measure of arc $ABC$?
I am stuck on how to draw this diagram and go about solving the problem. Do realise the answer must be $60$ degrees, but don't understand how. Any help will be appreciated.