# 15. Tycho wants to prepare a schedule for his exercise over the next few months. Every
week, he wants to exercise on the same days of the week. He does not want to exercise on
two consecutive days. He wants to exercise three days per week. How many schedules can he
choose from?
(A) 6
(B) 7
(C) 9
(D) 10
(E) 35​