****a computer networking question

Suppose that all datagrams have the same fixed length, that the switch operates in a slotted, synchonous manner, and that in one time slot a datagram can be tranferred from an input port to an output port. The switch fabric is a crossbar so that at most one datagram can be tranferred to a given output port in a time slot, but different output ports can receive datagrams from different input ports in a single time slot. What is the minimal number of time slots needed to transfer the packets shown from input ports to their output ports, assemblin any input queue scheduling order you want (i.e., it need not have HOL blocking)? What is the largest number of slots needed, assuming the worst-case sceduling order you can devise, assuming that a non-empty input queue is never idle?