Step-by-step explanation:
a) The equation in the form f(x) = ab^x represents exponential decay, where a is the initial value, b is the decay factor, and x is the number of years.
Given that the stock starts at $80 per share and decreases by 4% each year, the decay factor can be calculated as (1 - 0.04) = 0.96.
Therefore, the equation for the cost of the stock would be f(x) = 80 * 0.96^x.
b) To determine the cost of the stock after 5 years, we can substitute x = 5 into the equation:
f(5) = 80 * 0.96^5
Calculating this value gives us the cost of the stock after 5 years.
