An overflow spillway is 10 m long, between two square abutments, and has two piers of 0.25 m width on its crest, when the head over the weir is 0.6 m. the effective lengths of spillway for calculation of the discharge by the weir formula is
1
9.40 m
2
9.14 m
3
9.50 m
4
9.26 m