A 68-year-old man presents to the clinic for evaluation of progressive hearing loss, ringing in his ears, and facial pain on the left side. The symptoms started 1 month ago. He has also noticed some difficulty with his balance, but reports no falls. Pertinent physical findings are an unsteady gait and decreased hearing in the left ear. His eye movements, facial sensation, and facial movements are normal. An MRI scan of the brain reveals a tumor at the cerebellopontine angle. Which of the following cranial nerves is this tumor most likely to affect?