10. Consider the following expression P, written in postfix notation: P:12, 7, 3, -, /, 2, 1, 5, +, . + a. Convert Pinto its equivalent infix expression b. Evaluate the infix expression 11. What is the output from the following sequence of stack operations? Stack S; int x = 3, y = 8; S.push(9); S.push(x); S.push(y); x=S.popO; y=S.pop(); println(y); S.push(22); while(!S.StackEmpty) y = S.popO; println(y); println(x)