equivalence of Flat modules

Hi, All. I need to solve following exercise but i can not. Please help me solve it.

Exercise. For each R-module A establish the equivalence of the following conditions: (a) A is R-flat. (b) $Tor_1^R (A, R/I)$ for each left ideal I of R.

Thank you very much. I really appreciate your idea!

-
I think that MO is not the place for this kind of question, which looks like homework. See Matsumura, chap. 7, Th. 7.8 (3) for the commutative case. – Damian Rössler Sep 2 2011 at 9:51