The average life expectancy of tires produced by the Whitney Tire company has been 40,000 miles. Management believes that due to a new production process, the life expectancy of its tires has increased. In order to test the validity of this belief, the correct set of hypotheses is a. H_0: mu < 40,000 H_a: mu greaterthanorequalto 40,000 b. H_0: mu lessthanorequalto 40,000 H_a: mu > 40,000 c. H_0: mu > 40,000 H_a: mu lessthanorequalto 40,000d. H_0: mu greaterthanorequalto 40,000 H_a: mu < 40,000