An operating system uses $$shortest$$ $$remaining$$ $$time$$ $$first$$ scheduling algorithm for pre-emptive scheduling of processes. Consider the following set of processes with their arrival times and $$CPU$$ burst times (in milliseconds):

Process	Arrival Time	Burst Time
P1	0	12
P2	2	4
P3	3	6
P4	8	5

The average waiting time (in milliseconds) of the processes is ________.

Let A be a square matrix size $$n \times n$$. Consider the following pseudocode. What is the expected output?

C = 100; 
for i = 0 to n do 
for j = 1 to n do 
 { 
      Temp = A[ i ][ j ] + C ; 
      A[ i ][ j ] = A[ j ][ i ] ; 
      A[ j ][ i ] = Temp - C ; 
 } 

 for i = 0 to n do 
 for j = 1 to n do 
 output(A[ i ][ j ]);

Which of the following statements are CORRECT?

1) Static allocation of all data areas by a compiler makes it impossible to implement recursion.

2) Automatic garbage collection is essential to implement recursion.

3) Dynamic allocation of activation records is essential to implement recursion.

4) Both heap and stack are essential to implement recursion.

In the context of modular software design, which one of the following combinations is desirable?