The table below shows the fourth roots of different numbers:


Number (x) 16 16 81 81
Fourth root of the number (y) 2 −2 3 −3


Part A: Does the table represent y as a function of x? Justify your answer. (5 points)

Part B: The total cost f(x), in dollars, for renting a truck for x hours is shown below:

f(x) = 25x + 16

What is the value of f(20) and what does f(20) represent? (5 points)