If N is the algebraic difference of grades, S is the head light beam distance in metres, the length (L) of a valley curve, is

• A. <img src="/_files/images/civil-engineering/highway-engineering/35-16-154-2.png">
• B. <img src="/_files/images/civil-engineering/highway-engineering/36-16-156-2.png">
• C. <img src="/_files/images/civil-engineering/highway-engineering/36-16-155-4.png">
• D. <img src="/_files/images/civil-engineering/highway-engineering/36-16-155-3.png">
• E. <img src="/_files/images/civil-engineering/highway-engineering/36-16-156-5.png">