Answer:
Cost = $51.96
Explanation:
The radius of a regular hexagonal window, r = 2 feet
The area of a hexagonal shaped figure is given by :

Put r = 2 feet in above formula

Replacement glass for energy-efficient windows costs $5.00 per square foot. It means, the total cost will be :

So, the required cost will be $51.96. Hence, the correct option is (d).