Some aircraft component is fabricated from an aluminum alloy that has a plane strain fracture toughness of 35 MPa ?m. It has been determined that fracture occurs at a stress of 250 MPa when the maximum internal crack length is 2.0 mm. What is the "maximum" length of the surface crack you can tolerate for this same component alloy at a stress of 325 MPa? Assume the crack geometric constant to be 1.5?