To find the length of the diagonal of square C, we can use the Pythagorean theorem which states that in a right triangle, the square of the hypotenuse (the longest side) is equal to the sum of the squares of the other two sides. Since square C has equal sides, we only need to find the length of one side and then multiply it by the square root of 2 to get the length of the diagonal.
Using the coordinates given, we can find the length of one side by subtracting the x-coordinate of one vertex from the x-coordinate of the other vertex (11 - 1 = 10). We then multiply this by the conversion factor given in the problem (1 square unit = 25 feet) to get the length in feet (10 * 25 = 250). Finally, we multiply this by the square root of 2 to get the length of the diagonal (250 * sqrt(2) ≈ 353.55 feet).
Therefore, if square C has an area of 2500 square units and each unit is equal to 25 feet, then a square with a diagonal length of approximately 353.55 feet would be an accurate representation of square C.