What is the unit for the zero order rate constant?

For a certain reaction $R \to \text{Product}$, the plot of concentration $[R]$ vs time has a negative slope as shown. The order of reaction is:

Which of the following is the slope of the graph of $[A]_{t}$ versus time for a zero order reaction?

The decomposition of $NH_{3}$ on a platinum surface is a zero-order reaction. What are the rates of production of $N_{2}$ and $H_{2}$ if $k = 2.5 \times 10^{-4} \, mol \, L^{-1} \, s^{-1}$?

The rate constant of a zero-order reaction is $0.2 \ mol \ m^{-3} \ h^{-1}$. If the concentration of the reactant after $30 \ minutes$ is $0.05 \ mol \ m^{-3}$,then its initial concentration will be ....... $mol \ m^{-3}$.

In a zero-order reaction,if the initial concentration of the reactant is doubled,the time required for half the reactant to be consumed: