The calculated distance (air line) between Pyŏksŏng-ŭp and Haeju is approximately 9 miles respectively 14 kilometers.
By car or train, the actual journey to Haeju is certainly longer, as only the direct route (as the crow flies) between Pyŏksŏng-ŭp and Haeju has been calculated here.
Air line (approximately)
14 kilometers
7 nautical miles