$\backslash$table$[[$Month$,\backslash$table$[[$Hours of$],[$Maintenance$],[$Service$]],\backslash$table$[[$Maintenance$],[$Costs$]]],[$January$,520,$$ $4,640],[$February$,490,4,230],[$March$,280,2,720],[$April$,500,4,270],[$May$,320,3,030],[$June$,450,4,140],[$July$,340,3,020],[$August$,410,3,570],[$September$,470,4,040],[$October$,400,3,210],[$November$,360,3,260],[$December$,360,3,070],[$Total$,4,900,$$ $43,200],[$Average$,408,$$ $3,600]]$

Required:

Using the high$-$low method of cost estimation, estimate the behavior of the maintenance costs incurred by Nation's Capital Fitness, Incorporated. Express the cost behavior pattern in equation form.

Note: Round coefficient of $x$ to $2$ decimal places and other answer to the nearest whole dollar amount.

Monthly maintenance cost $=$