Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_36711 ( "Editor" text, "Site" text, "Style, clone of" text, "Cost ( US$ )" text, "Open source" text, "Activity" text )

### Question ###
Which source has a Cost free, and an Activity of some, and an Editor of markitup?

### Accurate SQL ###

SELECT "Open source" FROM table_36711 WHERE "Cost ( US$ )" = 'free' AND "Activity" = 'some' AND "Editor" = 'markitup'