A lightbulb has a normally distributed light output with mean 6000 end foot-candles and standard deviation of 100 end foot-candles.
a. Find a lower tolerance limit such that only 0.2% of the bulbs will not exceed this limit.
b. What fraction of these lightbulbs will have a lower than an output of 5920 end foot-candles?
c. If 50000 lightbulbs are made, how many of them will have an output stronger than 6180 end foot-candles? How many of them will have an output lower than 5890 end foot-candles?