Q. A 70-year-old man is found to have a right-sided oculomotor nerve palsy (ptosis, mydriasis, eye "down and out") and left-sided hemiparesis. An MRI reveals a lesion in the right midbrain involving the cerebral peduncle and the oculomotor fibers (which exit the midbrain anteriorly and medially). Which of the following best describes the likely location of the lesion?