In an axial flow compressor design, velocity diagrams are constructed from the experimental data of aerofoil cascades. Which one of the following statements in thios regard is correct?
(a) Incidence angle of the approaching air is measured from the trailing edge of the blade
(b) $\delta$ is the deviation angle between the angle of incidence and tangent to the camber line
(c) The deflection e of the gas stream while passing through the cascade is given by $\epsilon$= $\alpha _{1}-\alpha _{2}$
(d) $\epsilon$ is the sum of the angle of incidence and camber les any deviation angle, i.e.,
e= I + $\theta$ - $\delta$