9. A park is in the shape of a rectangle 8 miles long and 6 miles wide. How your walk if you walk diagonally across the park than along the two sides of it.

Look at the figure below: triangle abc is a right triangle with angle abc equal to 90 degrees. the length of ac is 5 units and the length of ab is 4 units. d is a point above c. triangle adc is a right triangle with angle dac equal to 90 degrees and dc parallel to ab. what is the length, in units, of segment cd?