What was found
(SUPPLEMENTAL MRR) PILOT REPORTED THAT AT BEGINNING OF DESCENT WHEN THRUST LEVERS WERE BROUGHT TO IDLE, THE SYSTEM 'B' HYDRAULIC LIGHTS ON F/O PANEL ILLUMINATED. BOTH SYS 'B' PUMP LOW PRESS LIGHTS ON F/O PANEL ILLUMINATED AND SYSTEM QUANTITY DROPPED TO ZERO. LOSS OF SYSTEM 'B' CHECKLIST WAS ACCOMPLISHED AND EMERGENCY DECLARED. UNEVENTFUL LANDING ACCOMPLISHED. REPLACED NR 2 SYSTEM 'B' ELECTRIC PUMP. REPLACED BR 1 SYSTEM 'B' PUMP, RAN BOTH PUMPS, OPS AND LEAK CK OK.