The magnitude of this number is far from 1, so it's low correlation
Since it's negative, so it's low negative correlation
Your max amount for this is $20. Let's say x represents the number of gallons.
20 ≥ 3.2x
x = 6.25 gallons
If they're asking for integers or whole numbers, you'd round down to 6 because you only have enough money for 6 full gallons. If you rounded up to 7, you wouldn't be able to fill it up completely because then you'd be over your $20.00 budget for gas.
Amplitude: 1/4 (= |a|)
Frequency: 1/2 (= |b|)
Period: 4pi (= 2pi/|b|)