Consider a simulation with average arrival rate of entities as lamba and three processes with average processing rates of u1, u2 and u3. Which of the following should be true to avoid an usntable system with growing queue?

a) If processes are in series, then ui+u2+u3 must be greater than lamba

b) if processes are in series then u1,u2,u3 muest be lower than lamba

c) if processes are in parallel, then ui+u2+u3 must be greater than lamba

d) if processes are in parallel, then ui,u2,u3 must be lower than lamba