Ammonium perchlorate $($NH$4$ClO$4)$ is a powerful solid rocket fuel, used in the Space Shuttle boosters. It decomposes into nitrogen $($N$2)$ gas, chlorine $($Cl$2)$ gas, oxygen $($O$2)$ gas and water vapor, releasing a great deal of energy. Calculate the moles of water produced by the reaction of $2\mathrm{.}1$ mol of ammonium perchlorate. Be sure your answer has a unit symbol, if necessary, and round it to the correct number of significant digits.