18. Simplify the following functional expressions using Boolean algebra and its identities. List the identity used at each step. a) y(xz+xz)+y(xz+xz) b) x(yz+y)+x(y+z) c) x[yz+(y+z)](xy+z) 19. Using the basic identities of Boolean algebra, show that x(x+y)=xy *20. Using the basic identities of Boolean algebra, show that x+xy=x+y 21. Using the basic identities of Boolean algebra, show that xy+xz+yz=xy+xz 22. The truth table for a Boolean expression is shown below. Write the Boolean expression in sum-of-products form. 23. The truth table for a Boolean expression is shown below. Write the Boolean expression in sum-of-products form. 24. Which of the following Boolean expressions is not logically equivalent to all the rest? a) wx+wy+wz b) w+x+y+z c) w(x+y+z) d) wxyz+wxy+wyz+wz