The result of solving the payment formula
`p=((P-D)r(1+r)^n)/((1+r)^n-1)`,
for price `P` is
`P=D+([(1+r)^n-1]p)/(r(1+r)^n)`.
In particular, when we substitute `D=2700`, `r=0.00325`, and `n=48` in both formulas, we get
`p = 0.0225P - 60.8`
for payment as a function of price and
`P = 44.4p+2700`
for price as a function of payment. Except for our rounding, the slopes `0.0225` and `44.4` are reciprocals of each other.