Questão de Português

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: "__________."