Exercise 9.4

For each pair of atomic sentences, give the most general unifier if it exists:

1. $P(A,B,B)$, $P(x,y,z)$.

2. $Q(y,G(A,B))$, $Q(G(x,x),y)$.

3. ${Older}({Father}(y),y)$, ${Older}({Father}(x),{John})$.

4. ${Knows}({Father}(y),y)$, ${Knows}(x,x)$.