Question

using the situation given, ask for permission, gire it and deny it informal
a) prepare a lemon nade
b) turn on the air conditioned
c) used your mobile phone

Answer 1

A.- Would you mind if I prepare a lemonade for lunch?
No. I don´t mind. Go ahead. Feel free to prepare the lemonade
Sorry, but we haven´t got much sugar as to spend it in a lemonade. Maybe next time.

B.- Is it ok if I turn on the air conditioner?
It is ok. You can turn it on.
No, It is consuming too much energy and we cannot afford to squander money on the electricity bill. 

C.- May I use your mobile phone?
Yes,of course, it is at your entire disposition.
I am sorry but you are not allowed to use my mobile phone for it is something which I consider very personal.