The area of a rectangle is thrice that of a square. The length of the rectangle is 40 cm and the breadth of the rectangle is (3/2) times of the square. The side of the square in cm is__________?

The area of a rectangle is thrice that of a square. The length of the rectangle is 40 cm and the breadth of the rectangle is (3/2) times of the square. The side of the square in cm is__________?

A. 15
B. 20
C. 30
D. 60