Annealing temp of Tm-2 in your case might work but frankly your primers are too short and thus have Tm's that are really too low:
Ideally for specificty and efficiency your primers should be 21-23bp and have a Tm of about 55-65 C
Thus, your primers Tm are about 10C too low
Have a go and try what has been suggested but if you find you get very little product or alternatively too many bands (on account of depressed annealing temp which might result in secondary non specific annealing) then re design your primers according to this Tm I prepared for students a few years back