(Building on what @akash.dinkar12 pointed)

it is a simple probability+PnC question, of type:

given n events E, P(E) = p and P(E') = 1-p,

Find the P(Success), where Success = exactly 1 event occurs.

it is a simple probability+PnC question, of type:

given n events E, P(E) = p and P(E') = 1-p,

Find the P(Success), where Success = exactly 1 event occurs.