Design a PDA to accept the following languages. You may accept either by final state or by empty stack, whichever is more conveinent.
a) {0^n 1^n | n >= 1}
b) The set of all strings of 0's and 1's such that no prefix has more 1's than 0's.
c) The set of all strings of 0's and 1's with an equal number of 0's and 1's.