Data Management easy fruit juice question

To make fruit juice, you buy apples, oranges, grapes, watermelon, lemons, pears, and bananas. How many different types of juice can you make if...
a) you choose any 3 types of fruit?
b) you choose any 3 types of fruit and one of them is apple?
c) you choose any number of different types?

Having trouble on c). Any help is appreciated, thanks so much!!

you say you're having trouble only with (c)

1 type: 7c1 = 7
2 types: 7c2 = 7!/2!5! = 21
3 types: 7c3
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upto 7 types; 7c7

you needn't actually calculate each separately
the sum of the binomial coefficients is 2^n
since 7c0 isn't included here (no juice !)
ans: 2^7 -1 = 127
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