实现结汇操作：外币→人民币

def solve():
    from pyodide.http import open_url
    offices_csv = open_url(____).read()
    staff_csv = open_url(____).read()
    currencies_csv = open_url(____).read()
    savings_products_csv = open_url(____).read()
    clients_csv = open_url(____).read()
    savings_accounts_csv = open_url(____).read()
    savings_account_transactions_csv = open_url(____).read()
    gl_accounts_csv = open_url(____).read()
    exchange_rates_csv = open_url(____).read()
    import sqlite3, pandas as pd
    from io import StringIO
    conn = sqlite3.connect(____)
    pd.read_csv(StringIO(____)).to_sql(____)
    usd_amount = ____
    fee_rate = ____
    rate = conn.execute(____).fetchone()[____]
    gross_cny = round(____)
    fee = round(____)
    net_cny = round(____)
    print(____)
    conn.close()