Example 3: An office machine is purchased for $5200. Assume that its salvage value, V, in dollars, depreciates, according to a method called double declining balance, by 20% each year and is given by V(t) = 5200(0.80), where t is the time, in years, after purchase. (a) Find V (5), and explain its meaning. (b) Find V'(5), and explain its meaning. (c) When will the salvage value of the office machine be half of the purchase price