The installment fee of Bank of Communications credit card is 0.72%, which is divided into 12 and 6 installments, but the principal payable in each installment is different, and the installment fee in each installment is the same.

Fee for each installment = installment principal × installment fee rate =4000×0.72%=28.8 yuan.

When it is divided into 12 installments, the principal payable in each installment =4000÷ 12=333.33 yuan, and the total payable in each installment is 362. 13 yuan.

Divided into six installments, the principal payable in each installment is 4000 ÷ 6 = 666.67 yuan, and the total payable in each installment is 695.47 yuan.