The credit card installment interest rate of Minsheng Bank is 2.6% for the third installment, 4.2% for the sixth installment, 6.3% for the ninth installment, and 7.2% for 12 installment.

Installment interest = total installment amount * installment interest rate, with the first installment paid in one lump sum.

Installment interest = 30,000/12 * 7.2% =180 yuan.

Repayment principal of each installment = total installment/installment.

The repayment principal of each installment = 30,000/12 = 2,500.

Thirty thousand 12 installment, total repayment amount = 30,000 * 7.2%+30,000 = 32160 yuan.