Prove the following

Let $\mathrm{X}=\overline{\mathrm{ABC}}+\mathrm{B} \overline{\mathrm{CA}}+\mathrm{C} \overline{\mathrm{AB}}$

Evaluate $X$ for

(a) $A=1, B=0, C=1$,

(b) $A=B=C=1$

(c) $A=B=C=0$.