Hello, (1) If the customer purchases according to scheme ①, it needs to pay 0.9 * 200 * x+0.9 * 40 * (4x+5) = 324x+180 yuan.

(2) If the customer purchases according to Scheme ②, it needs to pay 200X+40*(4x+5-x)=320x+200 yuan.

⑶ If x= 10, the calculation shows that the second scheme is more cost-effective.