Consider a 6-variable Boolean function f(x1, x2, x3, x4, x5, x6)-fi(x1, x2, x3, x4). f2(x4, x5, x6) where fi(x1, x2, x3, x4) = E(0,4,6.8,9,10,11,13,15) x1 is the most significant bit and f2(x4, x5, x6) = E(0,1,2) - x4 is the most significant bit. a) Obtain a minimal sum-of-product (SOP) expression for fi and fi with minimum literal counts. b) Obtain a minimal product-of-sum (POS) expression for f with a minimum literal count.