Q. Consider the pushdown automation (PDA) below which runs over the input alphabet (a, b, c). It has the stack alpabet {Zo,X} where Zo is the bottom-of-stack marker. The set of states of the PDA is (s, t, u, f) where s is the start state and f is the final state. The transitions of the PDA given below are depicted in a standard manner. For example, the transition (s, b, X) → (t,XZo) means that if the PDA is in states and the symbol on the top of the stack is X, then it can read b from the input and move to state t after popping the top of stack and pushing the symbols Zo and X (in that order) on the stack.
(s,∈,Zo→(f,∈)
(s,a,Zo)→(S,XXZo)
(s,a,X)→(S,XXX)
(s,b,X)→(t,∈)
(t,b,x)→(t,∈)
(t,c,x)→(u,∈)
(u,c,x)→(u,∈)
(u,∈,Zo)→(f,∈)
The language accepted by the PDA is