4 bells first begin to toll together with an intervals of 5, 10, 15 & 20 sec. How many times does they toll together in an hr?  Select
A) 40	B) 60	C) 80	D) 90	E) 110
5|5, 10, 15, 20   2|1, 2, 3, 4   |1, 1, 3, 2   L.C.M of 5, 10, 15, 20 is 60   60 times   60
<result>B</result>
4 bells first begin to toll together with an intervals of 5, 10, 15 & 20 sec. How many times does they toll together in an hr?