Please answer the last question of it.

2. RWC Incorporated has a monthly ledger balance and deposit float of $200,000 and $25,000, respectively. Regions Bank pays RWC an earnings credit rate of 40 basis points, the reserve requirement ratio is 10 percent, and there are 30 days in the month. If service charges are $500, what is the net service charge applied to RWC's DDA? To have no net service charge, how much must RWC hold in the DDA