Brand x batteries have a mean life span of 102 hours, with a standard deviation of 6.8 hours. brand y batteries have a mean life span of 100 hours, with a standard deviation of 1.4 hours. complete each of the sentences.

about 68% of brand x’s batteries have a lifespan between and hours. about 68% of brand y’s batteries have a lifespan between and hours. the life span of brand ’s battery is more likely to be consistently close to the mean.

You are the manager of a large crude-oil refinery. as part of the refining process, a certain heat exchanger (operated at high temperatures and with abrasive material flowing through it) must be replaced every year. the replacement and downtime cost in the first year is $165 comma 000. this cost is expected to increase due to inflation at a rate of 7% per year for six years (i.e. until the eoy 7), at which time this particular heat exchanger will no longer be needed. if the company's cost of capital is 15% per year, how much could you afford to spend for a higher quality heat exchanger so that these annual replacement and downtime costs could be eliminated?