Since line segment PQ passes through the centre O, so PQ is the diameter of the circle.
PQ=4 cm=2×OQ=2× radius,
On joining RQ. ∠PRQ=90∘ [∵ Angle subtended by diameter on the circle is 90∘]
∴∠ORQ=90∘−35∘=55∘
But, OR=OQ
∴∠ORQ=∠OQR=55∘
∴y=180∘−(55∘+55∘)=70∘ [Sum of angles of a triangle is 180∘]