First Order Reaction Questions

$t_{1/4}$ is the time taken for the concentration of a reactant to drop to $3/4$ of its initial value. If the rate constant is $K$, $t_{1/4}$ is:

In a first order reaction, the concentration of the reactant decreases from $0.8\text{M}$ to $0.4\text{M}$ in $15$ minutes. The time taken for the concentration to change from $0.1\text{M}$ to $0.025\text{M}$ is:

The half life period of a first order chemical reaction is $6.93\text{minutes}$. The time required for the completion of $99\%$ of the chemical reaction will be ($\log 2=0.301$):