How do I compute "earned income "as a self employed person to determine the maximum contribution I can make to a traditional IRA?

Hello, my single-member LLC's net profit in 2017 was $4,920 (Form 1040, line 12). Self employment tax was $695 (Form 1040, line 32).  I had no other earned income, and I have just one traditional IRA to which I have not yet made any contribution for 2017.  No special situations apply to me (for instance, I am not a reservist).  I am over age 50.

What is the maximum I can contribute to my traditional IRA for 2017 given these facts?  Thanks very much!