Now the problem is that this expansion does not match the given one. As a matter of fact, since is odd, there is no cosine series. So I'm starting to think this question is missing some initial details.
One possibility is that you're actually supposed to use the even extension of , which is to say we're actually considering the function
and enforcing a period of . Now, you should find that
The value of the sum can then be verified by choosing , which gives
We have been given that Grant spent $2.50, $4.00, $4.25, and $3.25 on breakfast in one week. The next week he spent $6 more in total for the 4 breakfasts than the week before. We are asked to find increase in the mean of second week.
Since Grant spent $6 more than last week, we will divide 6 by 4 to get how much mean of second week breakfast expenditures increased with respect to first week expenditures.
Therefore, mean of second week breakfast expenditure will be $1.5 more than first week.