what is the length of the length of the shear plane?

Question

If t = under formed chip thickness t_c =  chip thickness and$\varphi =$ shear angle, then what is the length of the length of the shear plane?     

(a) t sin $\varphi =$        (b) $t_{c} sin \varphi$ (c) t/sin $\varphi =$ (d) $t_{c} /sin \varphi$