The loan shall be repayable to the Contingent Fund of the Medical Board of California in equal or graduated periodic installments, according to a schedule agreed upon by the division and the borrower, over a 10-year period which shall begin three years after the student ceases to pursue a full-time course of professional instruction, excluding from such 10-year period all periods, up to three years, of (a) active duty performed by the borrower as a member of the United States armed forces, or (b) nonmilitary public services performed by the borrower which the division finds to be in the public interest.