The diagram below a circle, centre O. PQ is a tangent to the circle at Q and PTOR is a straight line. QRST is a cyclic quadrilateral in which angle RTS = 350 and RT and QS are diameters. Giving reasons for your answer, find the size of:

- Acute angle ROS.
- Angle RQS.
- Angle PQR.
- Angle QPT.
- Angle PQT.