Problem: find the number of different prime factors of 2400
Rationale: "explanation : l . c . m of 2400 = 3 x 2 x 2 x 2 x 2 x 2 x 5 x 5 3 , 2 , 5 number of different prime factors is 3 . answer : option c"
annotated_formula: add(const_2, const_2)