The answer would be 1440 feet^2, becasue for area you have to multiply the width, length, and depth. You bascally would draw a 3D rectangle and label the depth, height, and width. That would be your diagram.
So we can set up a right triangle in this situation with one of the legs being 21.4m and the height being 15m. Then we can use trigonometric formulas to find the angle of elevation of the sun.
Since we have the dimensions for the opposite and the adjacent sides, we can use the trigonometric function tangent to find the angle:

So let's plug this in:



However this is in radians - to convert to degrees, we must use the formula:

So then let's solve for degrees:



So now we know that the angle of elevation is 67.89°.
(4/5 #)/$3 = x/$10
x = (10/3)*(4/5 #) = 8/3 #
You can buy 8/3 pound for $10.