Final answer:
The cost of the wear on Gary's tires for driving 4000 km is $5, based on the initial cost of $80 per tire and a lifespan of 64000 km.
Step-by-step explanation:
Gary needs to calculate the cost of the wear on his tires after driving 4000 km. The tires cost $80 each and last for 64000 km. To find the cost of the wear, we'll use a simple proportion:
Cost of wear per km = Cost per tire / Tire's lifespan in km,
which is $80 / 64000 km = $0.00125 per km.
Now, for 4000 km, the cost will be: 4000 km * $0.00125/km = $5.
Therefore, the cost of the wear on the tires for the 4000 km trip is $5.