Predict, then run it

karts(kart, fee) = (k1,10),(k2,10). bookings(kart, grp) = (k1,g1),(k1,g2),(k2,g3). Total fleet value of karts booked this week — counting each kart once:

SELECT SUM(k.fee) AS value FROM karts k WHERE EXISTS (SELECT 1 FROM bookings b WHERE b.kart = k.kart);

Predict the exact output.