Geometry of a Circle Theorem: Urgent help appreciated.

Hi, I have one problem I am consistently stuck on.

A straight line meets two circles at the points A, B, C and D. The circles intersect at the points E and F. Find the size of angle BEC if angle AFD = 'alpha'.

This is the basic diagram:

http://i301.photobucket.com/albums/nn74/BL5965/6c.png

I have gone through and tried to make more sense of it. Please help me further to work this out. Thanks.

http://i301.photobucket.com/albums/nn74/BL5965/6ci.png

Thanks, BG