Answer:
28 ways
Step-by-step explanation:
After placing 1 ball in each of the seven bins, there are two balls left.
If we place both balls in a single bin, there are 7 different ways to place the balls (place both on bins 1 through 7).
If we place each of the remaining balls in a different bin, the number of ways to place the balls is:

The total number of ways to distribute those balls is 21 + 7 = 28 ways.
The pythagorean theorem is
. And since 2 and 5 are legs while c variable is the hypotenuse, the equation would be
, or the first option.
This link to a video will help
https://youtu.be/k3RwfEvqrB8