Convert from fotmal [lead] to tan [China]

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 (tan [China])
The tan is a traditional Chinese weight unit, now spelled dan in English transliteration. During the European colonial era the tan was equal to 100 cattys or 1600 taels. This is equivalent to 133.333 pounds, making the tan comparable to the European quintal as a commercial weight unit. In modern China the tan, or rather the dan, is equal to 100 jin, which is exactly 50 kilograms (110.231 pounds).