7.
At the metal-casting company where you work, you must
set up a conveyor system to move castings from the furnace
to the heat treatment area 55 yards away. The castings cool
at the rate of 0.3°F (degrees Fahrenheit) per second and
must not be allowed to cool more than 7°F before being
heat treated. What is the minimum speed, in feet per
second, that the conveyor must move?