I went to a place called American Car Care Centers to check my car for A/C
leak.  After "checking", I was told that there is a leak in the compressor
seal.  At the end, in addition to the labor for the check, I was charged 12
dollars for a pound of freon, although they evacuated my A/C afterwards
because of the leak.  First, is it fair for him to charge me for a pound of
freon ($12 plus tax) ?  Second, what can I do about this if this is unfair ?