19. Political Advertising Newspaper advertisements for political parties always have some negative effects. The recently elected party assumed that the three most important election issues, X, Y, and Z, had to be mentioned in each ad, with space x, y, and z units, respectively, allotted to each. The combined bad effect of this coverage was estimated by the party's backroom operative as B(x, y, Z) = x2 + 12 + 2z2 Aesthetics dictated that the total space for X and Y together must be 20, and realism suggested that the total space allotted to Y and Z together must also be 20 units. What values of x, y, and z in each ad would produce the lowest negative effect? (You may assume that any critical point obtained provides the minimum effect.)