chemical kinetics Questions

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 rate equation for the reaction $2\text{A}+\text{B}\to \text{C}$ is found to be: $\text{rate}=k[\text{A}][\text{B}]$. The correct statement in relation to this reaction is that the: