When the price of good A is $20, the quantity of good B purchased is 400. When the price of good A is $40, the quantity of good B purchased is 750. Using the midpoint rule, the cross price elasticity of demand between goods A and B is
(a) -0.91 and the goods are complements
(b) 0.91 and the goods are substitutes
(c) 1.10 and the goods are substitutes
(d) -2.20 and the goods are complements