formula for perimeter is: P=1/2 b•h

The cost of 97.5 square feet of glass is $1828.13

( Incredible! Who has a window that size in their house?!?! )

Step-by-step explanation:

The Area (not perimeter) is 1/2 b*h

To find the height if this equilateral triangle we can use the Pythagorean Theorem c² = a² + b²

The side of the triangle is 15; that is the hypotenuse, c

The base of the right triangle we need is 7.5

The altitude (height) is what we need to calculate.

15² = a² + 7.5²

225 = a² + 56.25   Subtract 56.25 from both sides, then take the square root to find a, that is h in the Area equation.

√168.25 = 12.99 . Round to 13

Calculate the Area = 1/2 b*h

15*13/2 = 97.5 square feet.

Multiply by the cost per square foot: $18.75

97.5 * 18.75 = 1828.125 . Round to $1828.13

it would be:

c.parallelogram.

the correct answers i think are b. and d.

give me brainliest if it is correct!