Determine how many different computer passwords are possible if: (a) digits and letters can be repeated, and (b) digits and letters cannot be repeated. 1. 3 digits followed by 4 letters.
2. 2 digits followed by 5 letters.

How do i start to solve? would appreciate a walk-thru! a bird sitting 16ft above the ground in an apple tree dislodges an apple. after how many seconds does the apple land on the ground? (assuming that no branches will interfere with it's fall)