Mausil and his K communities

Mausil is a real estate agent, belonging to Pajal. He has a plan to build a series of $M$ buildings in Pajal and for this he found a land which can accommodate $M$ buildings in a row one after another. The rule of the Pajal government is that no building in Pajal can have more than $N$ floors. Based on a few factors like cost of the land, water resources etc. the cost of constructing a building is