Assume that in the cost of tickets and transportation is the same as in the previous problem. A day of skiing at "Middle of Nowhere Resort" lasts $6$ hours, and a day of skiing at "Snow Paradise Mountain" lasts $12$ hours. Nataliya's budget is $$3000,$ and she would like to ski at least $720$ hours this season. What is the number of trips that she should do to these mountains in order to minimize the total cost of these trips?

$3\mathrm{.}1)1,2,3$

$3\mathrm{.}2)4,5$

$3\mathrm{.}3)8,9$

$3\mathrm{.}4)2$