Convert from firkin [butter, soap] to megatonne

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 (megatonne)
The megatonne is a metric unit of mass or weight equal to one million metric tons (tonnes), one teragram (Tg), or about 2.2046 billion pounds.