Exercise 6.2.5: PDA P = ({90,41,42,43, f},{a,b}, {20, A, B},8,90, 20, {f}) has the following rules defining 8: 8(90,a, Zo) = (21, AAZ.) 8(90, b, Zo) = (42,BZ) 8(90,, Zo) = (f, ) 8(91,a, A) = (41, AAA) 8(91,6, A) = (91,6) 8(91,, Zo) = (20, Zo) 8(42, a, B) = (93, ) 8(92,b, B) = (92, BB) 8(42,, Zo) = (20,20) 8(93,, B) = (92, ) 8(43, , Zo) = (91, AZ) Note that, since each of the sets above has only one choice of move, we have omitted the set brackets from each of the rules. *a) Give an execution trace (sequence of ID's) showing that string bab is in L(P). b) Give an execution trace showing that abb is in L(P). c) Give the contents of the stack after P has read b7a4 from its input. ! d) Informally describe L(P)