Question

A dairy cow can produce 5400 quarts of milk per year. Suppose there are about 8.9 million cows in the U.S.

Answer 1

If you're asking the amount of milk all cows in the U.S. can produce annually, multiply the quarts produced by a dairy cow and the number of U.S. cows:

5400 * 8,900,000 = 48,060,000,000

There are 48.06 billion quarts of milk produced by cows in the U.S.