Concept:
Mattavarani is a specific architectural term from the Natyashastra related to the construction of the classical playhouse (Prekshagriha).
Step 1: Analyzing the description of Mattavarani.
Assertion (A) correctly describes the Mattavarani as a side-veranda or portico, usually 8x8 hastas (translated here as feet) with four pillars, located on the sides of the stage (Rangapitha).
Step 2: Analyzing the function of Mattavarani.
Reason (R) is generally considered incorrect in this context. Traditionally, musicians in Sanskrit theatre sat between the two doors of the tiring room (Nepathya), not in the Mattavarani. The Mattavarani served more for structural beauty and as a transitional space.