stress in the link

Question

In the figure, the load P = 1 N, length L = 1 m, Young’s modulus E = 70 GPa, and the cross-
section of the links is a square with dimension 10 mm x10 mm. All joints are pin joints.

The stress (in Pa) in the link AB is ______________
(Indicate compressive stress by a negative sign and tensile stress by a positive sign)