A flat metal plate is exposed to fully-reversed tension-compression cycling (i.e., σmin = -σmax). If the initial surface crack length ao is 0.30 mm and the critical surface crack length ac is 3.5 mm, m is 3.0 (for a in m) and A is 2.0 x 10^-14 (for σ in MPa), estimate the maximum tensile stress to give a fatigue life of 3.0 x 10^7 cycles. Assume Y is constant at 0.90.
A) 73 MPa
B) 141 MPa
C) 119 MPa
D) 161 MPa
E) 101 MPa