Write a regular expression that describes L1. (5 points) Let L1 = {w E {a, b}* : every b in w is immediately followed by at least one a}. b) Write a regular expression that describes L2 (5 points) b. Let L2 = {WE{c,d}: w contains exactly once three consecutive d's and no additional pair of two consecutive d's. c) Write a regular expression that describes L3 (5 points) c. Let L3 = {wE{a,b}}: has start with at least two b's and finished with at least two a's. A/