The total area of the parking lot is 400 feet * 500 feet = 200,000 square feet.
Since only 80% of the area is usable for parking, the usable area is 200,000 square feet * 80% = 160,000 square feet.
If it takes 10 square feet to park a car, then the number of cars that can be parked is 160,000 square feet / 10 square feet per car = 16,000 cars.
#### 16000
The answer is: 16000
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
If James paves a new parking lot that measures 400 feet by 500 feet, and only 80% of the area is usable for parking, and it takes 10 square feet to park a car, how many cars can be parked in the parking lot?

### Answer:
