conditional expectation given sum

#1
Hello,

I need your help.
Suppose: \(X\sim N(0,\sigma^2_x)\), \( Y\sim N(0,\sigma^2_y) \), \( X, Y \) are independent, and \( c\in R\).
I need to find an expression (as closed form as possible) for:
\( E[X|X+Y>c] \).

Thanks!
Dan