In the diagram, line a is the perpendicular bisector of KM. Line a is a perpendicular bisector of line segment K M. It intersects line segment K M at point L. Line a also contains point N. Line segment K L is 6 x + 4. Line segment K N is 9 x minus 5. Line segment N M is 7 x + 7. What is the length of KM? 22 units 40 units 44 units 80 units