35 days. What fraction of these batteries would be expected to survive beyond 1000 days? 3.56. A light bulb has a normally distributed light output with mean 7500 end foot-candles and standard devi- ation of 100 end foot-candles. Find a lower specifica- tion limit such that only 0.5% of the bulbs will not exceed this limit. 3.57. The specifications on an electronic component in a target acquisition system are that its life must be between 5000 and 10,000 h. The life is normally distributed with mean 7500 h. The manufacturer realizes a price of $10 per unit produced; however, defective units must be replaced at a cost of $5 to the manufacturer. Two different manufacturing processes can be used, both of which have the same mean life. However, the standard deviation of life for process I is 1000 h, whereas for process 2 it is only 500 h. Production costs for process 2 are twice those for process 1. What value of production costs will determine the selection between processes 1 and 2?