Q2-1

Consider the following logic circuit whose inputs are functions $f_1, f_2, f_3$ and output is $f$

Given that $f_1(x,y,z) = \Sigma (0,1,3,5)$ $f_2(x,y,z) = \Sigma (6,7),$ and $f(x,y,z) = \Sigma (1,4,5).$ $f_3$ is