(1) A （0.05+ 0.02）*60*x = 4.2x B 50 + 0.02*60*x = 50 + 1.2x(2) 当 x = 20 时 A 4.2 * 20 = 84元 B 50 + 1.2*20 = 74元采用B方案较为合算
