Why ask Why?

Gabe is driving me mad with the constant 'Whys' in response to anything I say to him. It could be a simple task like take your shoes to your room and I get a why. I think it is good to ask questions when they are warranted but this is crazy. When I was teaching my co-teacher would respond with 'Why Not?' This just never seemed to work for me. Not to long ago when this started I was talking to a freind of mine who has three boys she told me her response is, "It's not why. It's yes Mam and you do it." This seems like a wonderful idea but it has been months and I am still having to deal with the whys. Though I can say, "What am I going to say." and Gabe will reply with, "It's yes mam." But having to do this every time is just as bad. Does anyone have any other tips or know when this usually stops? Please help I need some advice.