an engineer has designed a valve that will regulate water pressure on an automobile engine. the valve was tested on 170 engines and the mean pressure was 7.7 lbs/square inch. assume the standard deviation is known to be 0.8. if the valve was designed to produce a mean pressure of 7.6 lbs/square inch, is there sufficient evidence at the 0.01 level that the valve performs above the specifications? state the null and alternative hypotheses for the above scenario.