The answer should be 6z + 54 but I’m not completely positive.
<u>ANSWER</u>

<u>EXPLANATION</u>
The Cartesian equation is

We substitute


and

This implies that

Let us evaluate the exponents to get:

Factor the RHS to get:

Divide through by r²

Apply the double angle identity

The polar equation then becomes:

Substitute -2 in for x and get (9)^-2
Flip the equation so that the exponent is positive and get 1/9^2
Work it out 1/(9*9) = 1/81
That would be $1.50 per Gallon
525 divide 35 = 1515 times 1.38= 20.70 dollars