Answer: 
Step-by-step explanation:
Given
Propane produced heat energy of 
The volume of the tank is 
The energy produced by this propane tank is

$232400 Money earned in the next 7 years.
Money earned per year:
$33200 = 1st year
$35400 = 2nd year
$37600 = 3rd year
$39800 = 4th year
$42000 = 5th year
$44200 = 6th year
$46400 = 7th year
The tax and the total per night is calculated with $120 * 118%. You then will get $120*1.18, which is, $141.6. To get the tax alone, you can multiply $120 to 18%, and get $21.6.
Remember that percentages are basically a fraction over 100. (Ex. 18% is 18/100. You can simplify it to 0.18)
It will cost $21.6 in tax each night alone, but will cost $141.6 in total.