A transmission line has a span of 150 m between level supports. The cross-sectional area of the conduc tor is 1.25c * m ^ 2 and weighs 100 kg per 100 m. The breaking stress is 4220kg / c * m ^ 2 Calculate the factor of safety if the sag of the line is 3.5 m. Assume a maximum wind pressure of 100 kg per sq. metre.