Answer:
13.6 inches
Step-by-step explanation:
We can use Pythagorean theorem: 
Let c be the diagonal length, a for length, and b for width.
Substitute the values.

c=13.6 inches
Percentage of down payment that ABC bank requires to be paid = 20%
Price of the house = $10500
Then
Amount of down payment
that needs to be made = (20/100) * 105000
= 21000 dollars
From the above deduction, it can be deduced that the correct option among all the options that are given in the question is the third option or option "C". I hope that this is the answer that has actually come to your desired help.
In your question that ask to calculate the area of one of the tiles if a semicircular archway in the front of the garden is using 8 congruent granite tiles and the area of one of the tiles is 2.9ft ^2. I hope you are satisfied with my answer and feel free to ask for more.