In the figure shown, lines AB, CD, and EF are parallel. The length of AC is 2 units, the length of CE is 5 units, the length of AD is (2x + 1) units, and the length of DF is (3x + 6) units. Which is the length of AF?
15. 75 units
11. 25 units
4. 5 units
1. 75 units