Convert from firkin [butter, soap] to dekagram

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 (dekagram)
The dekagram is a common metric unit of mass, the dekagram is frequently used in European food recipes. One dekagram is equal to 10 grams, 0.01 kilogram, or 0.352 739 66 ounce. The symbol dkg sometimes used for this unit is incorrect.