I left my job in 2018, where I earned $3000 that year. At that point I had $500 in a 401k plan, which was too small to do a rollover to an IRA, so I cashed it out (after 20% tax I received $400, and paid another 10% early withdrawal when I filed). I did not make any other money that year (except for interest and dividends).
Now, I would like to max out my allowed Roth IRA contribution for that year, which is equal to my earned income (since it is below the max contribution limit of $5500). My question is: Is my "earned income" for that year $3000 or $3400 or $3500?