If two students, Lisa and Tom, interchange their seats, and Lisa is currently 8th from the top and 22nd from the bottom, what will be Tom's rank from the bottom if he is currently 15th from the top?
Answer: B. 21st
Tom's rank from the bottom is calculated as 50 - 15 + 1 = 36. After Lisa and Tom interchange, Lisa's new rank from the bottom is 21st.