Math application problem in the fourth grade of primary school: every New Year's calendar in 20 yuan, buy 4 copies and get 1 copy. Li Ming bought 34 copies at a time. How much cheaper can each serve be on average? 34 * 5 = 6 ...4 20 * 6 * 4 = 480 yuan 4+ 1=5 copies. 30-4+5 = 35 copies. 4' 20=80 yuan. 80+480=560 yuan. 20'35=700 yuan. 700-560= 140 yuan. 140 * 35 = 4 yuan. A: It's cheaper than 4 yuan on average.