[1 mark] 7. The Boolean function f= a + b + c-a can be written as: A. f=a(1 + w') C. f=a+b D. f a.(1.c) +b E. None of the above [1 mark] 8. Which one of the following is incorrect? A. x +0-x B. x.1=x C. x(x +y x D. (x+y)'=x,, y, E. None of the above