I have question about max. profit condition for monopolist block pricing.
I learned that to maximize profit in block pricing, given a linear demand curve function and constant MC, calculate $Q_2(Q_1)$, and $P_S(Q_1)$ then find $Q_1$ maximizing profit and then find $P_1$ and $Q_2$ the $P_2$.
This is what I read from the textbook (Microeconomic, Besanko).
But I heard somewhere that when in following case,
with right-downward sloping $MC$ and $AC$,
Profit maximizing first block price and quantity is $P_1$ and $Q_1$ where $AC=MR$ and second block price and quantity should be $P_2$ and $Q_2$ where $AC=D$
I've thought about this for 1 day and still couldn't get why maximizing condition is like that.