信用政策变更分析

def solve(____):
    sales_increase = new_sales - old_sales
    profit_increase = sales_increase * contribution_margin
    old_receivables = old_sales * old_days / ____
    new_receivables = new_sales * new_days / ____
    opportunity_cost = (____) * required_return
    bad_debt_increase = new_sales * bad_debt_rate
    net_benefit = profit_increase - opportunity_cost - bad_debt_increase
    return round(____)