Za report states that the cost of repairing a hybrid vehicle is falling even while typical repairs on conventional vehicles are getting more expensive. the most common hybrid repair, replacing the hybrid inverter assembly, had a mean repair cost of $3 comma 927 in 2012. industry experts suspect that the cost will continue to decrease given the increase in the number of technicians who have gained expertise on fixing gas-electric engines in recent months. suppose a sample of 100 hybrid inverter assembly repairs completed in the last month was selected. the sample mean repair cost was $3 comma 870 with the sample standard deviation of $500. complete parts (a) and (b) below. a. is there evidence that the population mean cost is less than $3,927? (use a 0.01 level of significance.)