$($CLO$-3/$PLO$-2$C$/C_2)$

Q$\mathrm{.}3.($a$)$ A specimen of $-$soil showed shear strength of $30K\frac{N}{m^2}$ under a normal stress of $42\mathrm{.}8K\frac{N}{m^2}.$ What will be angle of internal friction for the soil.

$10$