Bill thought of giving “The Hall of Operations” a visit, after listening to these interesting behaviors of the halls towards occupants from different rooms and houses.
He happened to visit the Hall from the back door entry and he saw 4 huge stones, one against each of the 4 halls (Addition, Subtraction, Multiplication and Division). Each stone had engravings on it describing the hall against which it is erected.
On one such stone, the following was engraved
“This hall has been and forever will be commutative for EVERY occupant of the “House of Rational Numbers, Q””.
This stone could correspond to which of the four halls?
Addition
Multiplication