月饼

def solve(n, demand, stocks, prices):
    stocks = list(map(float, stocks.split(',')))
    prices = list(map(float, prices.split(',')))
    demand = float(demand)
    items = [(prices[i] / stocks[i], stocks[i], prices[i]) for i in range(len(stocks))]
    items.sort(reverse=True)
    total = 0
    for ratio, stock, price in items:
        if demand >= stock:
            total += price
            demand -= stock
        else:
            total += ratio * demand
            break
    print(f'{total:.2f}')