In the synthesis of ammonia, if $-\Delta\left[\mathrm{H}_{2}\right] / \Delta t=4.5 \times 10^{-4}$ $\mathrm{mol} / \mathrm{L} \cdot \mathrm{min},$ what is $\Delta\left[\mathrm{NH}_{3}\right] / \Delta t ?$ $\mathrm{N}_{2}(\mathrm{g})+3 \mathrm{H}_{2}(\mathrm{g}) \longrightarrow 2 \mathrm{NH}_{3}(\mathrm{g})$