In the figure below,P,Q,R and S are points on the circle centre O. PRT and USTV are straight lines.Line UV is a tangent to the circle at S. <RST= 500 and <RTV=1500.

Calculate the size of

- < ORS
- <USP
- < PQR
- Given that RT=7cm and ST=9cm,calculate to 3 significant figures
- Length of the line PR
- The radius of the circle.