Find the missing character?

Start with the top left square and move clockwise around the others. The sum of the numerical values of the letters in each Circle follows the sequence 20, 25, 30 and 35.

A + C + D + L = 1 + 3 + 4 + 12 = 20
M + F + A + E = 13 + 6 + 1 + 5 = 25
L + H + D + K = 12 + 8 + 4 + 11 = 35.

So,
Q + I + B + ? = 30
17 + 9 + 2 + ? = 30
? = 30 - 28 = 2
Missing Character = 2 = B