[6.1 【新建订单】练习](6.1%E3%80%90%E6%96%B0%E5%BB%BA%E8%AE%A2%E5%8D%95%E3%80%91%E7%BB%83%E4%B9%A0.md) [6.2 【收款结算】练习](6.2%E3%80%90%E6%94%B6%E6%AC%BE%E7%BB%93%E7%AE%97%E3%80%91%E7%BB%83%E4%B9%A0.md)