EXPLANATION
Challenger cost = $14,000
Car depreciaton = 11%/yr = 0.11 (in decimal form)
A) The function that represents the value of David's car V(t) is the following:

Where y= value as a function of t, a= initial amount and r is the rate of depreciation.
Replacing terms:

B) Now, we can graph the function by drawing some points:
C) The car's value after 6 year would be given by pluggin in t=6 into the function:

Computing the power:

The value of the car after 6 years would be $6957.