A bakery prepares trays of muffins and scones each morning. Baking one tray of muffins takes 15 minutes, and baking one tray of scones takes 10 minutes. The oven can be used for at most 6 hours in a morning. If x is the number of trays of muffins and y is the number of trays of scones, which inequality represents the oven-time constraint for a morning?