Which of the following potential energy (PE) diagrams represents the $S_{N}1$ reaction?

$S_{N}1$  is two step reaction where in step (1) formation of carbocation takes place which is slow and requires more  $E_a$ is RDS.
1 is wrong as step (1) has less $E_a$  i.e., less formation of carbonation.
2 is wrong as it is P.E diagram of single step reaction 
3 is wrong as both steps have almost same  $E_a$.
P.E diagram for  $S_{N}1$