expected value of a segment of normal distribution

I need to find the expected value of a segment (namely the segment -infinity to C) of the normal distribution (the bell curve).

i know what i should integrate, I just cant integrate it as it is much too complicated for my small mind to handle.

basically Integral from -infinity to C of x times f(x) dx where f(x) is the pdf of the normal distribution which is much too complicated to write out on a board like this...

thanks a ton if you can get me this !

Norman