Ginza shopping mall bought back a batch of goods and priced them at 20% profit margin. Because of poor quality, they could only sell them at 80% of the price. How much was the loss of 400 yuan? Use it quickly!

Ginza shopping mall bought back a batch of goods and priced them at 20% profit margin. Because of poor quality, they could only sell them at 80% of the price. How much was the loss of 400 yuan? Use it quickly!

Let cost be x (1 -- 1.2 * 0.8 =: 0.04)
0.04X=400
X = 10000 yuan
Verification: 10000 * 1.2 * 80% = 9600 yuan, loss 400 yuan