B: The expression cons(x, y ) denotes the list formed by inserting the element x at the head of the list y. We denote the empty list by NIL; the list {2) by cons(2, NIL); the list {1, 2) by cons(1, cons(2, NIL); etc. The expression LASTx, y ) is intended to mean that y is the last element of the listx. We have the following axioms: (Vu) LAST(cons(u, NIL), u) (W) (Vy) (Vz)[ LAST( y, z ) ? LAST(cons(x,y ), z) ] (av) LAST(cons(2,cons(1, NIL)),v) (B2) Use answer extraction to find vthe last element ofthe list 2.11. longer lists