a. If the company sets the warranty at a year and a half (say 540 days), what proportion of calculators will they have to replace ? b . The company doesn't not want to replace more than 1% of the calculators they sell. What length of time should the set for the warranty ? c . The company would like to set the warranty for 540 days, and still replace no more than 1% of the calculators sold. Increasing the average life of the calculators is too expensive, but they think they reduce the standard deviation of the lifespans . What standard deviation of lifespans would be needed to make this happen ? d. Explain what achieving a smaller standard deviation means in this context.