A room has dimensions of 20 feet by 15 feet with a 10-foot high ceiling. There are six 200-cubic-feet-per-minute (CFM) registers supplying air to the room. How many air changes per hour take place in this room?

Python. primary u. s. interstate highways are numbered 1-99. odd numbers (like the 5 or 95) go north/south, and evens (like the 10 or 90) go east/west. auxiliary highways are numbered 100-999, and service the primary highway indicated by the rightmost two digits. thus, the 405 services the 5, and the 290 services the 90. given a highway number, indicate whether it is a primary or auxiliary highway. if auxiliary, indicate what primary highway it serves. also indicate if the (primary) highway runs north/south or east/west.