The two components of a two-tier rent form an indivisible whole. Setting the base rent does not fall within the jurisdiction of the commercial rent judge but is governed by the will of the parties, since the amount of rent under leases to be renewed must correspond to the rental value and no other value may be added to it (1st case); the contractual extension of the statutory regime makes no difference in this respect, since the parties may contract only in respect of rights they are free to dispose of (2nd case).