THE PILOT-IN-COMMAND'S FAILURE TO OBTAIN EMERGENCY ASSISTANCE AFTER BECOMING TEMPORARILY LOST, RESULTING IN TOTAL LOSS OF ENGINE POWER DUE TO FUEL EXHAUSTION. CONTRIBUTING TO THE ACCIDENT WAS THE DISPATCH OF THE STUDENT ON THE CROSS-COUNTRY FLIGHT BY THE CFI WITH AN ESTIMATED COMPLETION TIME OF 22 MINUTES AFTER THE OFFICIAL SUNSET. ALSO CONTRIBUTING TO THE ACCIDENT WAS THE LACK OF TOTAL EXPERIENCE BY THE PILOT.