If you are using "mac" to represent raincoats you are probably going to be okay, if you are thinking about various popular computers then I would suggest getting My100kCeaseAndDesistLetter.com as your next investment :p
Without knowing further information on your intentions nothing can be said on a valuation, so will say reg fee at this time...with a big flashing neon sign pointed at the door called grace delete.
Potential TM issues. However several independent Mac sites operate under domains including "mac" in the name so it all depends on your actual use. However I don't see much value in the name. $x - low $xx.