8.9 某家庭考虑购买某位置住宅公寓，总价为60万元，按开发商要求至少需首付20万元，剩余款项可申请银行贷款，假设贷款期限为30年，月利率为0.36%，建立模型预测等额还款时，月换款额时多少？

def calculate_monthly_payment(P, annual_interest_rate, n_years):
monthly_interest_rate = annual_interest_rate / 12 / 100
total_months = n_years * 12
M = P * (monthly_interest_rate / (1 - (1 + monthly_interest_rate) ** (-total_months)))
return M

loan_amount = 400000

annual_interest_rate = 0.36 * 12

loan_term_years = 30

monthly_payment = calculate_monthly_payment(loan_amount, annual_interest_rate, loan_term_years)

print(f"每月还款额为: {monthly_payment:.2f} 元")

print("学号后两位：04")