Read the following conversation and choose the best option to complete it:

Tourist: "Excuse me, could you tell me where the main entrance to the museum is?"
Guide: "Certainly! Just follow this path straight ahead, and you'll see the entrance on your left."
Tourist: "Thank you! Also, do you know if there's a guided tour available today?"
Guide: "Yes, there is. The next guided tour starts in about 15 minutes."
Tourist: "Great! Do you know how long the tour lasts?"
Guide: "_______________ ."