Need help writing a manual equation for a Chi-Square test for an assignment

So I am struggling a tad with a portion of my assignment to manually solve this version of the chi-squared equation. The section I am referring to is Part D in my code and the equation in the left picture. I cant think of how to incoorporate N into my equation, i know that right before i will set N=length(x) which is one of the columns in the given data. In my code the y is the yi in the problem's eq, F is mi and err_y is sigmi,i. Any help would be appreciated I have been stuck on this part for a couple hours and the result i got from running this is 15,837 which is a far cry from 0.