C Because the other answers 2 or1 pound that's more than the amount in the question asks for
Answer:

Step-by-step explanation:
Hello,
<u>The mean of five numbers is 8</u> so we can write

<u>When another number is added the mean is 7</u>, let s note x the another number we can write

From the first equation we can say

So the second equation becomes

The solution is then 2
Hope this helps
All you have to do for this is follow the midpoint formula.
Let me know if the picture is unclear and I'll type it out for you.
Each blade is 360/5=72° apart from the next blade, so you would need to rotate the top fan by at least 72° to again line up with the bottom fan.