Final answer:
To calculate the area of the shaded region of the trapezoid is 686 square units, use the formula (base1 + base2)/2 × height; however, the correct calculation is not reflected in the provided options.
Step-by-step explanation:
The area of the shaded region of the trapezoid with bases 23 and 26 units and height 28 units can be found using the area formula for a trapezoid, which is (base1 + base2)/2 × height. Plugging the given values into the formula, we get (23 + 26)/2 × 28 square units. This simplifies to 49/2 × 28, which equals 686 square units, but this answer is absent from the given options. There might be an error in the question or the options provided.