Answer is the last one, 5 over 36 gallons
Step by step
We know 5/9 gallons of popcorn
We know we will divide by 4/1
So 5/9 divided by 4/1
When we divide fractions we flip the divisor and multiply across
5/9 x 1/4 = 5/36 or 5 over 36 gallons
Problem solved