b$.$

$\backslash$table$[[$Month$,$Jul,Aug,Sep,Oct,Nov,Dec$],[$Forecast$,320,340,360,380,400,400],[$Output$,,,,,,],[,$ Regular,$300,300,300,300,300,300],[,$ Overtime,$20,20,20,20,30,30],[,$ Subcontract,$20,30,40,40,60,70],[$Output$-$Forecast,,,,,,$],[$Inventory$,,,,,,],[,$ Beginning,,,,,,$],[,$ Ending,,,,,,$],[,$ Average,,,,,,$]]$

c$.($Refer to part b$)$ After complaints from some workers about working overtime every month during the first half of the year, the manager is now corsidering adding some temporary workers for the second half of the year, which would increase regular output to a steady $350$ units a month, not using any overtime, and using subcontracting to make up needed output. Determine the total cost of that plan.