I am roasting two boneless turkey breasts. I understand that you should cook them to an internal temperature of 165F, but I do not have a meat thermometer. So, I wanted to get a general idea of how long they should cook and someone suggested 20 minutes per lb. But is this time for the total weight of the breasts or based on the individual weights of the breast. That is, should I cook based on a total weight of 3.5 lbs or a weight of 1.75lb/breast? Thanks.