Answer
a. No
b. Yes
Work Step by Step
a. This is impossible. Modeling the situation as a graph, where two people have an edge between them if they are friends, such a graph would need a total degree of 45, which is odd, so this is impossible as total degree of a graph must always be even. This is because addition of any edge to a graph adds 2 to its total degree (adds 1 to the degree of each vertex it touches). Therefore, this is impossible.
b. This is possible. consider the case where everyone is friends with each other. It satisfies the conditions.
