The following sequence of operations is performed on a stack:

PUSH (10), PUSH (20), POP, PUSH (10), PUSH (20), POP, POP, POP, PUSH (20), POP

The sequence of values popped out is:

Q. The following sequence of the operations is performed on a stack PUSH(10), PUSH(20), POP, PUSH(10), PUSH(20), POP, POP, POP, PUSH(20), POP the sequence of values popped out is

Q. The following sequence of operations is performed one a stack:
PUSH(10), PUSH(20).POP, PUSH(10), PUSH(20), POP, POP, POP PUSH(20), POP
The sequence of values popped out is

Q. Consider the following C program:

# include <stdio.h>
# define EOF - 1
void push (int); /* push the argument on the stack */
int pop (void); /* pop the top of the stack*/
void flag Error( );
int main ( )
{
int c, m, n, r;
while ((c = getchar ( ))! = EOF)
{
if (isdigit (c))
push (c);
else if ((c = = '+') | | (c = = '*'))
{
m = pop ( );
n = pop ( );
r = (c = = '+') n + m : n*m;
push (r);
}
else if ( c! = ' ')
flag Error ( );
}
printf("%c", pop( ));
}

What is the output of the program for the following input?

5 2 * 3 3 2 + * +

Q. The five items A, B, C, D and E are pushed in a stack one after the other starting from A. The stack is popped 4 times and each element is inserted in a queue then 2 element are deleted form the queue and pushed back on the stack. Now 1 item is popped from the stack the popped item is _________.

Q. An implementation of queue Q, using two stacks S1 and S2, is given below:

void insert(Q, x)
{
push(S1, x);
}
void delete (Q, x)
{
if (stack -empty (S2)) then
if ( stack - empty(S1)) then
{
print ("Q is empty");
return;
}
else while (! stack - empty(S1))
{
x = pop (S1);
push(S2, x);
}
x = pop(S2);
}

Let n insert and $(m\le n)$ delete operations be performed in an arbitary order on an empty queue Q. Let x and y be the number of push and pop operations performed respectively in the processes. Which one of the following is true for all m and n?