AAA Controls makes a switch that is advertised to activate a warning light if the power supplied to a machine reaches 100 volts. The voltages at which a warning occurs are normally distributed. A random sample of 75 switches is tested, and the mean voltage at which a warning occurs is 98 volts, and the standard deviation was 6 volts. a. Create a 90% confidence interval on the true mean voltage at which a warning occurs. b. Create a 95% confidence interval for the variance o?.