Yes, the function is exist.

Since the function P is one - to - one function.

Because the each population of U.S. corresponds to exactly one particular year.

Yes, the function is exist.

Yes, the function is exist.

Since the function P is one - to - one function.

Because the each value of population of U.S. corresponds to exactly one value of year.

The represents the each value of year corresponds to exactly one value of population of U.S.

The represents the each value of year corresponds to exactly one value of population of U.S.

The function is exist.

The represents the each value of year corresponds to exactly one value of population of U.S.

The value of  .