A certain type of lightbulb has an average life of 500 hours, with a standard deviation of 100 hours. the length of the bulb can be closely approximated by a normal curve. an amustment park buys and installs 10,000 such bubls. fin the total number that can be expected to last each periof of time.

(a) less than 500 hours

(b)at least 500 hours

(c) between 680 and 780 hours

(e)less than 770 hours

(f)more than 440 hours

(G) find the shortest and longest lengths of life for the middle 60% of the bulbs