I'm sorry, but the chemical formula for ammonium carbonate is not NH.HCO.
The correct formula for ammonium carbonate is (NH4)2CO3.
In this case, the formula should indicate that there are two ammonium ions (NH4+) for every one carbonate ion (CO3^2-), resulting in the formula (NH4)2CO3.
So, the correct match for the chemical name "ammonium carbonate" is with the formula (NH4)2CO3.