For a portion of national highway where a descending gradient of 1 in 25 meets with an ascending gradient of 1 in 20, a valley curve needs to be designed for a vehicle travelling at 90 kmph based on the following conditions. (i) headlight sight distance equal to the stopping sight distance (SSD) of a level terrain considering length of valley curve> SSD. (ii) comfort condition with allowable rate of change of centrifugal acceleration = 0.5 m/sec3. Assume total reaction time = 2.5 seconds; coefficient of longitudinal friction of the pavement= 0.35; height of head light of the vehicle =0.75 m; and beam angle = 1°. What is the length of valley curve (in m)based on the comfort condition? __________