Question $18(1$ point$)$

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$4\mathrm{.}2-1$a$.$ Packet scheduling $($FCFS$).$ Consider the pattern of red and green packet arrivals to a router's output port queue, shown below. Suppose each packet takes one time slot to be transmitted, and can only begin transmission at the beginning of a time slot after its arrival. Indicate the sequence of departing packet numbers $($at $t=1,2,3,4,5,6,7)$ under FCFS scheduling. Give your answer as $7$ ordered digits $($each corresponding to the packet number of a departing packet$),$ with a single space between each digit, and no spaces before the first or after the last digit, e$.$g$.,$ in a form like $7654321).$

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