Answer:
Harry will take 21 seconds.
Step-by-step explanation:
Speed of Harry =

Since, Harry covers 12 miles in 6 minutes,
Then the speed of Harry =

= 2 miles per minute
If he covers 0.7 miles then time taken by him will be,
Time taken =

=

= 0.35 minutes
≈ 0.35 × 60 seconds
= 21 seconds