How can I determine the relative contribution of predictors in multiple regression model?

Sure. Thanks for getting back to me.

So lets say ‘y’ - made profit.
x1 - number of times comercial was shown on channel 1
x2 - number of times comercial was shown on channel 2

xn - number of times comercial was shown on channel n

I want to know how much each channel contribute to the a profit.

Example:
My profit is $3000 and 20% comes from channel x1, 30% comes from x2, n% comes from Xn.

This is what I mean contribution of each predictor to target in %.
Thank you.