Answer:
5
Step-by-step explanation:
A function

where a is the initial value and b is the multiplicative rate of change.
In the function,

5 is the value of b so
5 is the multipicative rate of change
I think you would divide each by 2 and get 1 over 1 which would be 1 squared over 1 (negative) cubed
Hope this helps!
If he only filled up five containers, then he would only have one and 1/4 gallons of oil
note that :
cot150 = 1/tan150
cos390 = cos(360+30) = cos30