In 2001, the mean household expenditure for energy was $1493, according to data obtained from the U.S. Energy Information Administration. An economist wanted to know whether this amount has changed significantly from its 2001 level. In a random sample of 35 households, he found the sample mean to be $1618 and the sample standard deviation to be $321. Test the claim that the mean expenditure has changed siginificanlty from the 2001 level at the 0.05 level of significance. State your conclusion