A shopping mall has 8 branches in a city. Branch B7 is 5 km north of Branch B5. Branch B2 is 8 km east of Branch B7. Branch B3 is 8 km west of Branch B8. Branch B2 is 14 km north of Branch B8. Branch B4 is 6 km west of Branch B6. Branch B1 is 5 km north of Branch B4. Branch B5 is 12 km east of Branch B1. What is the direction of branch B4 with respect to branch B7?