某工厂用如图甲所示的长方形和正方形纸板做成如图乙所示的竖式与横式两种长方形的无盖纸盒

(1)
假设 竖纸盒 x 个,横纸盒 (100 - x) 个
正方形纸：竖纸盒 = x, 横纸盒 = 2 * (100 - x),一共 x + 2(100 - x) = 200 - x
长方形纸：竖纸盒 = 4x, 横纸盒 = 3 * (100 - x),一共 4x + 3(100-x) = 300 + x
(2)
正方形纸：200 - x 38 342 < 5y < 358
=> 68.4 < y < 71.6
y = 69, 70, 71
=> (x, y) = (24, 69), (22, 70), (20, 71)
(24, 69)：4x+3y = 96 + 207 = 303
(22, 70)：4x+3y = 88 + 210 = 298
(20, 71)：4x+3y = 80 + 213 = 293
因此 a = 293, 298, 303