This is the original equation multiplied through by `M`.
We subtracted `ln(P_0/(M-P_0))` from each side.
The difference of logs is the log of the quotient.
We exponentiated both sides of the equation.
We multiplied across by `P_0(M-P_0)`.
We expanded the product on the right-hand side.
We gathered the terms with `P` as a factor together on the left-hand side and factored `P` out.
We divided both sides by `M-P_0+P_0e^(Mkt)`.