question: In what stage did Jaime Vergara won, Team Classification was given to EPM-Une and Mountain Classification winner was Oscar Solis?
answer: SELECT stage FROM table_28853064_15 WHERE team_classification = "EPM-UNE" AND mountains_classification = "Oscar Solis" AND winner = "Jaime Vergara"
context: CREATE TABLE table_28853064_15 (stage VARCHAR, winner VARCHAR, team_classification VARCHAR, mountains_classification VARCHAR)