Im pretty sure it is when there is an uneven number
That would be A :D It would be A because you would do keep change flip. You would keep 5/6, change the division sign to multiplication, then flip the 5/16 to 16/5 (the reciprocal)
The volume of the box in this problem doesn't really matter, considering that a cereal box is hollow. Assuming the surface area is 174 inches², then you can simply multiply 0.05 x 174, which is 8.7. Then put that number in the form of money to get $8.70. (seems a bit pricey for one cereal box to me ;P)
You can try using the formula y=mx+b