$3.$ Identify the functional dependency rule for each of the following items:

a$.$ If X $->$ Z and X $->$ Y$,$ then X $->($Z$,$Y$).$ What functional dependency rule does this demonstrate?

b$.$ If A $->$ B and B $->$ C$,$ then A $->$ C$.$ What is the name for this type of functional dependency?

c$.$ Use a formula like the above to show the decomposition rule.