CREATE TABLE table_13705 ("Outcome" TEXT, "Date" TEXT, "Tournament" TEXT, "Surface" TEXT, "Opponent in the final" TEXT, "Score in the final" TEXT)

What is the score in the final of the tournament with a clay surface on 18 April 2011?
SELECT "Score in the final" FROM table_13705 WHERE "Surface" = 'clay' AND "Date" = '18 april 2011'
SELECT "Score in the final" FROM "table_13705" WHERE "Date" = '18 april 2011' AND "Surface" = 'clay'