How did the use of standard currency, or coins, the economy of the roman empire?
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The answer is:

People would trade for Roman coins even if they did not want Roman goods.

why was the national assembly formed by the third estate?

the estates-general had not been assembled since 1614, and its deputies drew up long lists of grievances and called for sweeping political and social reforms. the third estate, which had the most representatives, declared itself the national assembly and took an oath to force a new constitution on the king.

d. she conquered the black sea coast and parts of poland.