Question

a) Consider a single-server Q with LIFO (last-in-first out) services. Suppose that three customers show up at times 5, 6, and 8, and that they all have service times of 4. When does customer 2 leave the system?

(a) 3;
(b) 9;
(c) 13;
(d) 17;
(e) 19

Answer 1

As we started at time t=0

So there was no customer till t=5 hour

At t=5 customer first came and as there was no other customer so we started service to customer1

As service take time off 4 hour so service to customer1 will end at t=9 hour.

Also mid-time at t=6 customer2 came and at t=8 customer3 came.

As we have to use LIFO(later come first out ) pilicy so we service first customer3 then customer2

At t=9 we started service to customer3 and it end at t=13 hour(4 hours later)

Now at t=13 hour we started service to customer2 and it end after four hour at t=17

therefore customer2 leaves at t=17 hours.option(D)