1. A license plate has 4 letters followed by 3 single digit numbers (i.e. 0, 1, 2, ...9). How many possible license plates are there? 2. (a) How many 2 letter passwords can be formed using the letters {A, B, C, D} (w/ repetition allowed)? (b) How many 2 letter passwords can be formed using the letters {A, B, C, D} w/o repetition? Record all the possibilities and show how you would fill out the appropriate formula. (c) Organize your results above into groups so that each group contains only different permutations of the same combination of letters. (d) How many ways can a sample of 2 letters be chosen from {A, B, C, D} without repetition. Record all the possibilities and verify that your answer is correct using the appropriate formula.