Repayment of any loan and interest authorized under this chapter shall be made monthly and shall begin not later than nine months after the date the student borrower is last enrolled in a participating institution or any other institution of higher education. The board may, however, authorize a longer period before beginning repayment of loans to medical students, dental students, and other students seeking professional or graduate degrees. The board may extend the time for beginning repayment for unusual financial hardships, with the approval of the attorney general. Repayment shall be made directly to the board pursuant to a contract executed by the board in accordance with its rules and regulations.