Final answer:
The width of the dog run is 29 feet, and the correct option is not provided in the given choices.
Step-by-step explanation:
Let the length of the dog run be L and the width be W. The formula for the perimeter of a rectangle is P = 2L + 2W. In this case, the length is given as 40 feet, and the total amount of fencing used is 98 feet. Setting up the equation 98 = 2(40) + 2W, we can solve for the width W.
Simplifying, we get 98 = 80 + 2W, and subtracting 80 from both sides gives 2W = 18. Dividing both sides by 2, we find W = 9. Therefore, the width of the dog run is 9 feet. However, none of the given options match the correct width. It seems there might be a discrepancy in the provided choices.
In conclusion, the width of the dog run is 29 feet, and the correct option doesn't appear to be among the choices given.