An inflow hydrograph is routed through a reservoir to produce an outflow hydrograph. The peak flow of the inflow hydrograph is $P_I$ and the time of occurrence of the peak is $t_I$. The peak flow of the outflow hydrograph is $P_O$ and the time of occurrence of the peak is $t_O$. Which one of the following statements is correct?

1. $P_I <P_O$ and $t_I < t_O$
2. $P_I <P_O$ and $t_I > t_O$
3. $P_I >P_O$ and $t_I < t_O$
4. $P_I >P_O$ and $t_I > t_O$