Convert from firkin [butter, soap] to obol, obolos, obolus [Greece]

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 (obol, obolos, obolus [Greece])
The obol, obolos, obolus [Greece] is a historic unit of weight or mass. The obol is a very small weight that originated as the weight of a tiny Greek coin. In modern Greece, the obolos is an informal name for the decigram (0.1 gram).