A structural member is made from a steel that has KIc = 180 MPa√m and yield, strength 1050 MPa. In service it should neither break nor deform plastically, be- cause either would be considered a failure. Assume f = 1.0. If there is a preexisting surface crack of a = 4 mm, at what stress will the structural member fail? Will it fail by yielding or fracture?