Discount for the poor from tithe money

I work in video production. Right now, I’m working on a presentation for a poor widow. Can I give her a discount, and subtract the difference from the tithe that I take out of my income? A similar question: I was asked to make a presentation for a family where the father is very ill, and the whole household is in dire straits. Can I give them this presentation for free, and count the hours that I spent working on it as part of my tithe?  

Dear …

Yes, you can subtract these expenses from your tithe account. But you have to let them know what the original price was, and how much of a discount (or a gift) you are giving them.