Ineed asap! i just need on these 2 i don't understand!

tyrell wants to use the fermi process to estimate the number of blueberries that would fit in an empty city bus. as part of the process, he needs to estimate the volume of a typical city bus. he figures that a city bus is 40 ft long, 10 ft wide, and 10 ft tall

which estimate is the best approximates the volume of the bus ?
a) 4 × 10^1 ft^3
b) 4 × 10^2 ft^3
c) 4 × 10^3 ft^3
d) 4 × 10^4 ft^3

elisa wants to use the fermi process to estimate the number of ping pong balls that would fill a truck. as part of the process, she needs to estimate the volume of a ping pong ball. the diameter of a ping pong ball is about 40mm.

what estimate best approximates the volume of a ping pong ball ?

a) 3× 10^3 mm^3
b) 3× 10^4 mm^3
c) 3× 10^5 mm^3
d) 3× 10^6 mm^3