Two Supports, Made of the Same Material and Initially of Equal

Multiple Choice

Two supports, made of the same material and initially of equal length, are 2.0 m apart. A stiff board with a length of 4.0 m and a mass of 10 kg is placed on the supports, with one support at the left end and the other at the midpoint. A block is placed on the board a distance of 0.50 m from left end.As a result the board is horizontal. The mass of the block is:

A) zero
B) 2.3 kg
C) 6.6 kg
D) 10 kg
E) 20 kg