A natural gas pipeline failed in the middle of a farmer's field in Saskatchewan and subsequently ignited. Fortunately, no one was injured but the failure lead to an extensive failure analysis. The original design was conducted assuming that the steel being used had a fracture toughness of 80 P√m. The operating pressure of the pipeline was measured to be 16 P when the failure occurred. A post-mortem inspection revealed a semielliptical surface crack normal to the hoop stress was the fracture initiation site. The elliptical crack was observed to have a total length of 2 = 10 mm and a depth of, c = 4mm. Given the diameter of the pipe was 1 m and the wall thickness = 15 mm, calculate the in-service fracture toughness of the steel. The yield stress of the pipe was measured to be 670 Pa