Chemical Kinetics

For a first order reaction the concentration of reactant was reduced from $0.03 \mathrm{molL}^{-1}$ to $0.02 \mathrm{molL}^{-1}$ in 25 min . What is its rate (in $\mathrm{molL}^{-1} \mathrm{~s}^{-1}$ )?