Beth began a 16-day exercise program by doing 5 sit-ups on the first day. If she does 6 sit-ups on the second day, 7 sit-ups on the third day, and if each day thereafter she does 1 more sit-up than on the previous day, what is the total number of sit-ups that Beth will do during the 16-day program?
a) 126
b) 200
c) 210
d) 410
e) 420
a) 126
b) 200
c) 210
d) 410
e) 420