Convert from fotmal [lead] to sack [UK, wool]

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 (sack [UK, wool])
The sack [UK, wool] is a traditional unit of weight, varying for different commodities shipped in sacks. In Britain, for example, the sack was a traditional measure for wool, fixed by Edward III at 364 pounds (26 stone) in 1340.