6. Define the universal set, Q, as Q = {x: 0 :::: x :::: 5 or 10 :::: x :::: 20}, and define the following subsets of Q as Al = {x: 0:::: x < 2.5}, A2 = Ix: IS < x :::: 20}, A3 = {x: 2.5 :::: x :::: 5 or 10 :::: x :::: 20}, A4 = {x: 0 :::: x :::: 5 or 10 :::: x :::: IS}.

In addition, define the following two index sets as It=(l,3}, 12= {l,4}.