63A [Seller's notice fixing additional final period for buyer's performance];

64A21 [Seller's right to avoid contract: buyer does not pay within an additional period set by the seller];

76B [Avoidance: damages based on current price];

81C [Effect of avoidance: restitution by each party of benefits received];

82B3 [Application to seller by analogy of principle that buyer's inability to return goods in same condition: buyer loses right to avoid unless good sold or transformed by buyer in normal use];

84B [Upon avoidance buyer must account to seller for benefits from goods]