Based on my little knowledge of statistics
4.
It's 8!/4!= 1680
(the exclamation point is basically the number of probabilities in the combination)
5.
(speculation) It's 10!-6!= 3,628,080
plus
8!-6!=39,600
equals
(3,628,080 + 39,600) / 6! = 5094
(the 6! is the amount of drink combinations you are limited to)
FYI- you can use the exclamation mark on your phone calculator, either swipe to side or press the ''extras'' button