TSBT would like to maintain their cash account at a minimum level of $45,000, but expect the standard deviation in net daily cash flows to be $5,000; the effective annual rate on marketable securities to be 4.5 percent per year; and the trading cost per sale or purchase of marketable securities to be $50 per transaction. What will be their optimal cash return point?

$44,809.47

$55,754.24

$64,809.47

$73,431.54