How many N's are there in the given letter series which are immediately followed by exactly 3 consecutive M's? N, M, M, M, N, M, M, N, M, N, M, M, M, N, M, N, M, M, N, M, M, N, M, M, M

Complete the following alphanumeric series: N7V, K9T, H12R, ?, B21N

Find the next term in the alphanumeric series: Z1A, X2D, V6G, T21J, R88M, ?

Find the missing term (?) in the following alpha-numeric series: A2B, B3D, C5F, (?), E11J