The challenge with the Korean Money Market Hedge is that it is a payable - a payable form a Korean won cash balance. A MM Hedge for a payable is to simply transfer money into the target currency at the start of the period (the front end of the box), and then to have that money earn interest on deposit for the time period until payment is due.

In this problem, that means transferring enough Korean won at the start to fund a dollar deposit which will yield a total of $30 million at the end of 90 days. The dollar deposit earns a deposit rate (not a borrowing rate). The won transferred out of the account at the beginning of the period then reduces the account balance, which then earns the Korean interest rate for the 90 days to get to an ending cash balance.