Problem : A 5"X5" plate with a crack size of 2a=1.5" is under a spectrum load as shown below. The plate has a yield strength of 75 ksi and the crack growth is governed by da/dN = 1.6 x 10-8(ΔK)4, where AK is in a unit of ksi-in1/2. The finite width correction factor for SIF is Y(a/W) = √sec(Πa/W). Determine the crack growth for cycle #3 using Wheeler's retardation model (m=2).