Convert from rotl, rotel, rottle, ratel [Arab] to carat [international]

Unit Definition (rotl, rotel, rottle, ratel [Arab])
The rotl, rotel, rottle, ratel is a traditional Arab unit of weight corresponding to the Roman libra, the French livre, and the English pound. There was considerable variation in the unit from time to time and from place to place, but usually the rotl was about 0.9-1.15 pound (450-530 grams). However, in some areas of the Near East, such as Syria and Palestine, larger rotls of 5.5 to 6 pounds (2.5-2.8 kilograms) were used. This unit has many spellings in European languages.

Unit Definition (carat [international])
The carat [international] is a unit of mass used for diamonds and other precious stones. Originally spelled karat, the word comes from the Greek keration, a carob bean; carob beans were used as standards of weight and length in ancient Greece in much the same way barleycorns were used in old England. Traditionally the carat was equal to 4 grains. The definition of the grain differed from one country to another, but typically it was about 50 milligrams and thus the carat was about 200 milligrams.