Related to CLRS Exercise 6.2-2: Write a Python function min_heapify(arr, i) that takes a list arr representing a binary tree and an index i as inputs, and modifies arr so that it represents a min-heap with the value at index i satisfying the min-heap property. Assume that the left and right subtrees of index i are already min-heaps. Do not use any helper functions to access the left child index, right child index, or parent index of a given index i. Instead, use basic arithmetic to compute these indices.