Explanation:
a) The range at which the internal temperature can rise is from 2°F to 6°F, which means that in order fo the final temperature of the turkey to fall within the range of 165-170°F, we need to pull remove the turkey when the internal temperature is at a minimum of 164°F or a maximum of 168°F.
b) I'd rather err on the higher side of the internal temperature. After all, no one eats poultry cooked medium rare due to the high probability of salmonella poisoning and the 165-170°F is meant to destroy the microbes that causes food poisoning. Not only that, poultry meat gets sufficiently cooked at that range.