There are ten possible digits (0 to 9).
If they can be repeated, you're looking at 10 * 10 *10 * 10 * 10, or 105
This means 100000 possible zip codes if repeatable.
If not, you're looking at one less each time:
10 * 9 * 8 * 7 * 6
90 * 56 * 6
540 * 56 = 30240 zip codes without any repetitions.
To complete path means the disc lands on the ground, the height f(t)=0
-18t²+42t+36=0
simplify by dividing -6: 3t²-7t-6=0
facotor: (t-3)(3t+2)=0
t=3 or t=-2/3 (discard this negative one because time cannot be negative.
so the answer is 3 seconds.
