WASHINGTON, May 24 (AFP) - The International Monetary Fund on Monday approved a 51-million-dollar loan installment for Pakistan, a Fund spokesman said here. The disbursement followed a review of Pakistan's economic reform program. Pakistan authorities and the IMF last November worked out a 5.5-billion dollar loan package aimed at helping the cash-strapped country resolve its balance of payments difficulties. The Fund approved a disbursement of 575 million dollars in January.  