Exercise 2.45. Let be given the function f(x1, x2, x3, x4) = x1x2∨x2x3∨

x3x4 ∨ x4x1. However, it is not defined for (1110) and (1111).

1 Find the set of four functions that meet this partial specification.

2 Find the function ϕ(x1, x2, x3, x4) for this situation.

3 Represent the four possible functions by means of f(x1, x2, x3, x4) and

ϕ(x1, x2, x3, x4).