Adam Company uses the FIFO method in its process costing system. The following information for the Assembly Department was obtained from the accounting records for September $($all materials are$)$ added at the beginning of the process$)$:

$\backslash$table$[[,$Number of Units,Percent Completed$],[$Work in process inventory, Sept. $1,60,000,],[$Started during the month,,$],[$Work in process inventory, Sept. $30,40,000,],[,,],[$Beginning work in process inventory,,$],[$Cost added during the month,,$]]$

a$.$ What was the amount of costs transferred out for September?

b$.$ What was the cost of ending work$-$in$-$process inventory?

c$.$ How much did the total costs per unit increase or decrease in September compared to August?