The first map shows a plot of that function. On the second map, to the
right, we have circled the two essential prime implicants that we found by
considering 1’s on one layer with 0’s in the corresponding square on the
other layer, ABCEand ABCE. The group of eight 1’s, CE (also an
essential prime implicant), is shown in brown on the third map (where the
essential prime implicants found on the second map are shown as don’t
cares). Groups of eight have three literals missing (leaving only two). At this
point, only two 1’s are left uncovered; that requires the essential prime
implicant, BCD, shown on the fourth map in tan.