What is the equation to calculate the number of symmetric keys needed, and how many keys are required if 10 people need to communicate using symmetric keys?

A.
N(N+1)/3 and 40 keys are needed

B.
N(N-1)/2 and 45 keys are needed

C.
N(N/2) -1 and 35 keys are needed

D.
N(N+1) and 25 keys are needed

Explanation:
The correct equation to use to determine how many symmetric keys are
needed is N(N-1)/2. If 10 people needed to communicate via symmetric encryption
processes, then 45 keys are needed.