Convert from firkin [butter, soap] to picogram

Unit Definition (firkin [butter, soap])
The firkin [butter, soap] is a traditional unit of weight for butter and soap, equal to 4 stone or 56 pounds (about 25.40 kilograms).

Unit Definition (picogram)
The picogram is a metric unit of mass equal to 10E-12 gram or one millionth of a microgram.