Solve this:
In the figure below, O is the centre of the circle and angle QPR = x^o ;  angle ORQ y^o. Which statement is true about x^o and y^o ?

(a) x^o+y^o=120^o                 (b) x^o+y^o=180^o
(c) x^o+y^o=90^o                   (d) x^o+y^o=150^o