If the operation € is defined for all x and y by the equation x € y = 3*x*y, then 3 € (4 € 5) = Choose the correct choice from the following answers:
A) 80  B) 120  C) 160  D) 540  E) 660

Rationale: "working inside out , ( 4 € 5 ) = 3 * 4 * 5 = 60 3 € 60 = 3 * 3 * 60 = 540 hence , answer is d"
Answer: D