Angles in a Circle: Finding Relationships with Diameter and Chord

Let $AB$ be the diameter of a circle with centre $O$. Point $K$ lies on the circumference of the circle.
a) Determine the angle $\angle KOA$ if $\angle KVA = 26^\circ$.
b) Determine the angle $\angle KVA$ if $\angle KOA = 26^\circ$.