Total for one week = 2100 kcal. If the loss of 3500 kcal is equal to a loss of 1.0 lb, for the amount of exercise that Charles did for one week, how much weight, in pounds, did he lose?
a) 0.3 lbs
b) 0.6 lbs
c) 0.9 lbs
d) 1.2 lbs