15-6 Currently, it takes five days from the time customers mail payments until Shark Bait Rafts (SBR) deposits them. SBR would like to set up a lockbox collection system that would reduce this collection float by three days. If SBR receives an average of $2,500 in payments per day and its opportunity cost is 18 percent, how much should SBR be willing to pay each month for the lockbox system