Given segment aed and bfc, ae=bf and ed=fc prove ad=bc What is 4???

Given: [tex]\overline{AED}[/tex] and [tex]\overline{BFC}[/tex], AE = BF, and ED = FC.
We prove that AD = BC as follows:

          Statement                                                       Reason

1. [tex]\overline{AED}[/tex] and [tex]\overline{BFC}[/tex]                                                    Given


2. AE + ED = AD                                        Segment Addition Postulate
    BF + FC = BC

3. AE = BF and ED = FC                                            Given

4. BF + FC = AD                                                    Substitution

5. AD = BC                                                      Transitivity property