折现回收期计算

def solve(____):
    cumulative = ____
    for t, cf in enumerate(____):
        discounted_cf = cf / (____ + discount_rate) ** t
        cumulative += discounted_cf
        if cumulative >= initial_investment:
            payback = t - ____ + (initial_investment - (____)) / discounted_cf
            return round(____)
    return float(____)