Assume a queue has been implemented "efficiently" with $2$ STACKS. How many pop operations would have happened when performing the following queue operations $($assume this is before the queue is deleted$)?$ Assume that the Queue was initially empty.

enqueue$(8)$

dequeue$()$

enqueue$(6)$

enqueue$(7)$

front$()$

enqueue$(5)$

dequeue$()$

enqueue$(3)$

enqueue$(0)$

front$()$

enqueue$(9)$

dequeue$()$