Problem 2. [3 points] The plane strains can be expressed, in terms of derivatives of displacements, as av Exx Ox' = Eyy dy' Yxy av Ju =1+ If the displacements in x- and y-directions occur such that v(x, y) = -au(x, y) where a > 0, and if strains were measured as xx = 2 x 10-6 = 2, y = -1.5, Yxy = 1.5u, what is the value of a?