Multiplant Monopoly With Third Degree Price Discrimination
Hint.
The following are the necessary conditions for profit maximization:
Monopoly with 1 plant and 1 market: $MR = MC$
Monopoly with 1 plant and 2 markets: $MR_1=MR_2=MC$
Monopoly with 2 plants and 1 market: $MR = MC_1=MC_2$
I'll let you figure out the rest.