A large flat plate is subjected to constant amplitude uniaxial cyclic tensile and compressive stresses. Compute the critical crack length if the fatigue life must be at least 3x106 cycles. Assume the initial maximum edge surface crack length to be 1.1 mm, and a maximum tensile stress of 160 MPa. Assume m=3.0, A=1.4x10-13MPa in meter units, and Y=1.2.