Top 4 qualify, winners of CL qualify, winners of Europa qualify but only a maximum of 5 from England, or any association, can participate in the Champions League but not by finishing 5th. What does that mean for us given that City and Chelsea are in the semis of the Champions League and Arsenal and United are in the semis of the Europa? Well, it is a bit fraught given that 4th seems more attainable than 3rd.
If Arsenal win the Europa League then they will take a slot. If Chelsea then finish outside the top 4 and somehow win the Champions League then its bye bye Champions League and hello Europa League for the 4th place team.