In every 3 days, it gains = 11 min = 660 sec
So, In 1 day, it gains = 660/3 = 220 sec.
Now, For 5 days, it would be: = 220 × 5 = 1100 sec
We Know, 1 min = 60 sec.
So, 1100 sec = 18 1/3 min.
So, Your Final Answer would be 18 min. 20 sec
Hope this helps!