Please help emergency and add explanation too pleaSE

What is not true about kl and mn? what is mn? (show )

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?

Pls the last one and it has to be like number 6