The rate constant for a first order reaction is 60 s^(-1). How much time will it take to reduce the initial concentration of the reactant to its l/16^(th) value?

The rate constant for a first order reaction is 80 s^-1 . How much time will it take to reduce the concentration of the reactants to 1/18^(th) of Its initial value ?

The rate constant for a first order reaction Is 90 s^-1 .How much time will it take to reduce the concentration of the reactant to 1/20^(th) of its Initial value ?

The rate constant for a first order reaction in 60S^(-1) . How much time will it take to reduce the concentration of the reactant to 1/(20^(th)) of its initial value ?