Twenty-five heat lamps are connected in a greenhouse so that when one lamp fails, another takes over immediately. (Only one lamp is turned on at any time.) The lamps operate independently, and each has a mean life of 90 hours and standard deviation of 2 hours. If the greenhouse is not checked for 2,275 hours after the lamp system is turned on, what is the probability that a lamp will be burning at the end of the 2275-hour period