The cost of a Frigbox refrigerator is $850, and depreciates $40 each year. The cost of an Arctic Air refrigerator is $1350 , and it depreciates $140 per year.

(a) Find an equation for the value of the Frigbox, $F$, $t$ years after it is purchased.
$F(t) =$

(b) Find an equation for the value of the Arctic Air, $A$, $t$ years after it is purchased.
$A(t) =$

(c) If a Frigbox and an Arctic Air are bought at the same time, when do the two refrigerators have equal value?
In years.