The formation width of a highway with no transverse slope on an embankment is B. The height of the embankment is d and side slope of the embankment is S: 1 The area of cross-section of the embankment is
1
B + d + S × d
2
B × D + S × d
3
B × d + S × d2
4
\(\frac{1}{2}\left( {B\times d + S{d^2}} \right)\)