## Make an array 1
1. Return the integer array `{2,5,10,20}`.
2. Return the String array `{"Fast","Fish","Frying","Food"}`.
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## Make an array 2
* Make an array with n zeros.
* Fill it with the numbers 0 through (n-1).
fill_a(6) == {0,1,2,3,4,5}
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## Make an array 3
* Make an array with 2n zeros.
* Fill it with integers, counting up from 21.
fill_b(3) == {21,22,23,24,25,26}