There are six processes waiting in ready queue with the burst time are 9 , 7 , 4 , 2 , 1 and x . In what order should they run to minimize the average waiting time when the value of x is either 5 or 6.
a) 1 , 2 , 4 , x , 7 , 9
b) 9 , 7 , x , 4 , 2 , 1
c) x , 7 , 9 , 4 , 2 , 1
d) order cannot be decided