CREATE TABLE table_name_28 (prothrombin_time VARCHAR(255), partial_thromboplastin_time VARCHAR(255), platelet_count VARCHAR(255), bleeding_time VARCHAR(255))
Which Prothrombin time has a Platelet count of unaffected, and a Bleeding time of unaffected, and a Partial thromboplastin time of normal or mildly prolonged?
    
SQL: SELECT prothrombin_time FROM table_name_28 WHERE platelet_count = "unaffected" AND bleeding_time = "unaffected" AND partial_thromboplastin_time = "normal or mildly prolonged"