## monotone likelihood ratio

How do i show the sum of (Xi-Mu )^2 is a monotone likelihood ratio for a normal distribution with mu known and variance unknown. I know that I need to find the function for (X1, X2,...Xn) then to find the ratio do fn(x given sigma^2 one)/fn(x given sigma ^2 two) and then simplify to show it relies on the sum of (Xi-mu)^2.
Could someone just help me with finding the function of (X1,X2,...Xn)? And any hints how to simplify the ratio??