HOMEWORK 2.
Exercise 2.1 (from the book).

Say whether the following goals would succeed, and which variables, if
any, would be instantiated to what values:

pilots(A,london) = pilots(london,paris)
point(X,Y,Z) = point(X1,Y1,Z1)
letter(C) = word(letter)
noun(alpha) = alpha
'vicar' = vicar
f(X,X) = f(a,b)
f(X,a(b,c)) = f(Z,a(Z,c)