A polymer plate is under a stress of 150 MPa. To determine the largest internal crack length on the plate, the document uses the fracture toughness of 5.0 MPa-m1, Young's modulus of 1.2, and yield strength of 150 MPa in the fracture toughness formula. By plugging these values into the formula and solving, the document determines that the largest internal crack length is 0.246 mm.