4. Consider a probability space with four elements, we call a, b, c, and d (i.c., 1 = {a, b, c, d} ). The o-algebra F is the collection of all subsets of 0; i.e., the sets in F are n, {a, b, c}, {a, b, d}, {a, c, d}, {b, c, d}, {a, b}, ta, ch, (a, d}, (b, c}, {b, d}, {o, d}, (a}, (b}, (o}, {d), 0