A local record store had cassettes on sale for eight dollars each and compact disc on sale for $11 each. They sold 100 more compact testing cassettes. If the total sale was 3068 then how many cassettes did they sell

Monitors manufactured by tsi electronics have life spans that have a normal distribution with a standard deviation of 1800 hours and a mean life span of 20,000 hours. if a monitor is selected at random, find the probability that the life span of the monitor will be more than 17,659 hours. round your answer to four decimal places.