$2\mathrm{.}69$ A $1-$in$.$ square was scribed on the side of a large steel pressure vessel. After pressurization the biaxial stress condition at the square

is as shown. Knowing that $E=29{10}^6$ psi and

$u=0\mathrm{.}30,$ determine the change in length of $(a)$ side $AB,($b$)$ side $BC,($c$)$ diagonal

$AC.$