For this case we have the following product:

We must use the distributive property correctly to solve the problem.
We have then:

Then, we must add similar terms.
We have then:
Answer:
The final product is given by:
option 2
I feel like there is something missing from this question, for example how large is the tree house? If these are just plain measurements, then I would opt for B.
Hey there! I'm happy to help!
First, let's find the radius. The radius is half of the diameter.
8.4/2=4.2
Here's how to find the area of a circle.
Square the radius.
4.2²=17.64
And multiply by pi (3.14 in our case)
17.64(3.14)=55.3896
We round to the nearest tenth, giving us an area of 55.4 ft²
Have a wonderful day! :D