People arrive with poisson process with Rate 2

Find

(C) P( N(1) = 2 Given N(3) = 6)

For this i Said this was equal to N(2) = 4 and worked it out using formula.

(D) This one is driving me crazy.

P N(1) (Greater than or =) 2 Given N(1) (Greater than or =) 1

Help With D and confirmation on C would be greatly appreciaded. Thanks!