Consider a flat plate of some metal alloy that is to be exposed to repeated tensile-compressive cycling in which the mean stress is 25 MPa. If the initial and critical surface crack lengths are 0.15 and 4.5 mm, respectively, and the values of m and A are 3.5 and 2 x 10^-14, respectively (for change in stress and a in m), estimate the maximum tensile stress to yield a fatigue life of 2.5 x 10^7 cycles. Assume the parameter Y has a value of 1.4, which is independent of crack length.