How do I calculate the volume???

Given the following statements, which is the best

An unknown number of kids and buses are getting assigned. when assigning 4 kids to each bus, there are 2 kids that aren't placed in a bus. when assigning 8 kids to each bus, there are 2 empty buses. how many total kids are there?

Arectangle has a width of 9 units and length of 40 units. what is the length of a diognal. a. 31 unitsb. 39 unitsc. 41 units d. 49 units