A 48-year-old man with primary biliary cirrhosis presents with easy bruising and bleeding from his gums for the past two weeks. He also notes mild numbness and tingling in his hands and feet and has experienced difficulty seeing at night. Physical examination reveals ecchymoses on his arms and legs and scattered petechiae. Laboratory studies show a prolonged prothrombin time of 24 seconds (reference 11–15 seconds) with a normal activated partial thromboplastin time. Serum testing demonstrates low levels of vitamins A, D, E, and K. Which vitamin deficiency is most likely responsible for this patient’s coagulopathy and prolonged prothrombin time?