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The drying time of a type of paint under specified test conditions is known to be normally distributed with a mean value of 75 min and a standard deviation of 9 min. Chemists have proposed a new additive desinged to decrease average drying time. It is believed that dry- ing times with this additive will remain normally distributed with o = 9. Because of the expense associated with the additive, evidence should strongly suggest an improvement in av- erage drying time before such a conclusion is adopted. Let a denote the true average drying time when the additive is used. The appropriate hypotheses are Ho : / = 75 versus Ha : p