SAT Right triangles Question

For a certain type of rope, the equation $y=900a{x}^2$ , where $a$ is a constant, gives the estimated breaking strength $y$ , in pounds, of a rope with a circumference of $x$ inches. Based on this equation, if a rope of this type has a circumference of 0.75 inches, it has an estimated breaking strength of 708.75 pounds. What is the estimated breaking strength, in pounds, of a rope of this type that has a circumference of 4.50 inches?