Abarter economy
a. employs moneychangers.
c. exchanges goods and services.
b. uses coins of different values.
d. uses bills of exchange

Aliter of water contains about 3.35 x 10^25 molecules. a certain river discharges about 2.9x 10^8 l of water every second. about how many molecules does the river discharge every minute? write your answer in scientific notation