Convert from gros to libra [ancient Rome]

Unit Definition (gros)
The gros is a traditional French weight unit equal to 3 deniers (about 3.824 grams).

Unit Definition (libra [ancient Rome])
The libra [ancient Rome] is a traditional unit of weight. The libra was the Roman unit from which the English pound is descended; the symbol "lb" for the pound comes from this unit. The Roman libra contained only 12 unciae (ounces) and was about 0.722 English pound. The word "libra" is sometimes used now for the kilogram, a much larger unit.