Convert from vagon [Yugoslavia] to firkin [butter, soap]

Unit Definition (vagon [Yugoslavia])
The vagon is a traditional unit of mass or weight in countries of the former Yugoslavia. Originally considered to be the weight that could be carried by a wagon, the unit has been "metrized" and is now defined to be equal to the dekatonne, that is, 10 metric tons or 22 046.23 pounds avoirdupois.

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).