Find the missing couple of letters in the following series .

Question

AZ, GT, MN, ? , YB

Answer 1

Answer should be SH

Explanation
A - First Letter from Start
Z - Last letter from end

G - seventh letter from start (1+6)
T - Seventh Last Letter

M - 13th letter from start (7+6)
N - 13th from last

S - 19th letter from start (13 + 6)
H - 19th from last