Hi, can I get help with this question? I believe my approach to this question is wrong.
I converted 1 hour to 3600 seconds and calculated the time required to play the entire tunes, then divided the 3600s to the latter.
The correct answer is C 
Q37) I have a bird automaton that, when activated, flaps its wings and whistles three different tunes successively, selected at random from its repertoire of ten. It performs one of its ten tunes for 10 seconds, six of them for 15 seconds each and three of them for 20 seconds each.
When my granddaughter visits she is fascinated, activating it again and again as soon as it stops each time. On her last visit she kept it going for a whole hour and I lost count of how many times she activated it.
What is the maximum number of times that my automaton could possibly have been activated during one hour?
A) 75
B) 80
C) 90
D) 120
E) 225