It is given that at each router we encounter 5 packets. That means at each router we will have to wait for 5*Tt+self Tt = 6Tt
now there are 9 routers. So total delay = 6*9*Tt = 54Tt
now we also have to add Tt for sender to transmit that packet
so total delay now becomes 54Tt + Tt = 55*Tt
now Tt=1100/64 = 17.1875 msec
total delay = 55 * 17.1875 = 945.3125 msec