I want to hang out with my friend on Sunday (or some other time), what is the correct way to ask him about his ability to do it?
a)"Are you free on Sunday?" or b)"Will you be free on Sunday?"
I can feel the slight difference in the meaning of these two phrases (present continuous is used for asking about plans, while future simple doesn't), but I don't completely understand it. Is there real difference and what phrase should I use?