AARP claims the average annual expenditure for americans age 50+ on restaurant food in 2008 was $2130. Suppose a 2018 study randomly sampled 32 Americans age 50+ and found an average expenditure on restaurant food of $1945 with a standard deviation of $800. IS there a reason to believe that the average annual expenditure for americans age 50+ on restaurant food has decreased since 2008 at a=.01? what is the null hypothesis?