Two Identical Concrete Slabs Lie Flat and in Contact with Each

Multiple Choice

Two identical concrete slabs lie flat and in contact with each other as shown in the figure. If the temperature increases by 40°C, the lower edges opposite the contact edges remained fixed in position, and the lower edges of the contact side remain in contact, at what angle will the slabs be tilted? The coefficient of thermal expansion of the concrete is 10 × 10^-6/K.

A) 19°
B) 0.028°
C) 15°
D) 1.6°
E) The answer depends on the length of the slabs.