Calculate the critical crack size (a) for σ = σys, σys/2, and σys/4 for an edge crack in a 4.00-inch thick infinite plate in a material that has σys = 100 ksi and Kic = 120 ksi (in.)(1/2).
a) 0.63 inches, 1.26 inches, 2.52 inches
b) 1.26 inches, 2.52 inches, 5.04 inches
c) 2.52 inches, 5.04 inches, 10.08 inches
d) 5.04 inches, 10.08 inches, 20.16 inches