Question

4. Forrest Lumber uses the function
S(t) = -105t + 525

to determine the salvage value S(t), in dollars, of a table saw t years after its purchase. How long will it take the saw to depreciate completely?
6 years
-5 years
5 years
4 years

Answer 1

should be 5

Answer 2

Every year it deprecates by $105, so divide the year 0 value;
S(0) = 525
by the deprecation per year
$105
and get 5 years