Set Theory Questions

In a diagram:
1. Rectangle shows people who eat Apples
2. Ellipse shows people who eat Bananas
3. Triangle shows people who eat Cherries



Which letter(s) in the diagram represent those people who eat only bananas (neither apples nor cherries)?

If $A$ and $B$ are two sets where the number of elements in set $A$ is $28$, the number of elements in set $B$ is $35$, and the number of elements common to both sets $A$ and $B$ is $12$, determine $n(A\cup B)$.