Convert from fotmal [lead] to quartern

Unit Definition (fotmal [lead])
The fotmal is a traditional English unit of weight for lead. In medieval England the fotmal was equal to 70 "mercantile" pounds, which is equivalent to 72 avoirdupois pounds.

Unit Definition (quartern)
The quartern is a traditional English unit of weight equal to 1/4 stone, 3.5 pounds, or about 1.5876 kilogram.