Maintenance order cost flow

Hi...Gurus .....

My client want the maintenance cost as per the process wise, so can you explain how the cost arriving via the maintenance work order.

i have 3 work centers :- Mechanical, electrical & Tool.

in my Work center i assigned the Cost Center :- Main01 , but in my equipment i assigned the cost center :- Extrusion-01 (Dept cost Center).

how the cost flows from the order .