In a certain medical group, Dr. Schwartz schedules appointments to begin $30$ minutes apart, Dr. Ramirez schedules appointments to begin $25$ minutes apart, and Dr. Wu schedules appointments to begin $50$ minutes apart. All three doctors schedule their first appointments to begin at $8{:}00$ in the morning, which are followed by their successive appointments throughout the day without breaks. Other than at $8{:}00$ in the morning, at what times before $1{:}30$ in the afternoon do all three doctors schedule their appointments to begin at the same time?
I'm not sure how to approach this question. They all begin at the same time at $8{:}00$. Also doesn't the overlapping of appointments depend on how long their respective appointments take?