The International Monetary Fund's board approved a $77 million emergency loan to Lebanon on Monday night to rebuild the country following last year's war between Israel and Hizbullah guerrillas. The loan, set at a low interest rate of 5.25 percent, represents a small fraction of Lebanon's $40 billion of debt, equivalent to about 180 percent of its annual economic output. It is intended as a transition loan to a larger IMF package under discussion for implementation next year, according to Mohsin S. Khan, director of the fund's Middle East and Central Asia Department. Khan said the size of the larger package has not been determined. Khan said the money would be made available to Lebanon immediately.