67.5 square feet
Working
A = 1/2*base*height
A = 1/2*15*9
A = 67.5 sq. feet
Answer: $1526.28
I = (3634)(0.06)(7)
I = 1526.28
When using percents, make sure to divide it by 100 and use that (0.06 instead of 6 in this problem)
If t varies inversely with the speed, the formula for that is

. If t = 2 and r = 40, then we can solve for k, the constant of variation. Multiply both sides by 40 to get k = 80. Now we need to find the value for t when r = 45. Using the k value we just solved for, we will fill in the equation as

for a t value of about 1.78 hours