The American number format

Dear students
I have received messages about the American number format in §©roblem 2b. I would like to point out that the samples consists of elements greater than 1, the sum of the observations is 517, so the sum of the squares of these elements cannot be less than 517. But many of you were confused by the position of the point. So I will consider only the basic steps and main formulas in this problem. So, this missunderstanding will be taken into account during grading.