先付年金现值

def solve(pmt, rate, nper):
    pv_ordinary = pmt * (1 - (1 + rate) ** (-nper)) / rate
    pv_due = pv_ordinary * (1 + rate)
    return {"年金": pmt, "利率": rate, "期数": nper, "先付年金现值": round(pv_due, 2)}