Each of the capital letters in bold in this 3x3 grid is to be substituted by a different digit from 1 to 9 such that :

• Each of A, C, G and I is even, and:
• The sum of the digits in each of the four 2x2 subgrids is equal.

A   B   C
D   E   F
G   H   I

Disregarding the rotations and reflections, how many distinct solutions are there?