I have attached an image of a k-map of 5 variables ABCDE that I have. I don't understand why the implicants circled in red or green are is an essential implicant? According to my understand of grouping in K-map, all 1s must be circled. So wouldn't either the red or green circled region one of the essential implicants so that cell no. 7 will be covered? Thanks.