An Ethernet switch has eight ports and all ports must be operational for 24 hours...

To calculate MTTR, we need to convert the hours into minutes. Here are the steps:

Monday: Port 7 was down from 4 PM to 11 PM. That’s 7 hours or 420 minutes.

Wednesday: Port 7 was down from 2 PM to 10 PM. That’s 8 hours or 480 minutes.

Friday: Port 7 was down from 5 AM to11 AM. That’s 6 hours or 360 minutes.

Total corrective maintenance time = 420 + 480 + 360 = 1260 minutes

Number of repairs = 3

MTTR = Total corrective maintenance time / Number of repairs

MTTR = 1260 / 3 = 420 minutes

Therefore, the MTTR of Port 7 is 420 minutes.