This is not a diet. It's a simple way to lose weight. And you don't even have to give up the food you love or join a gym (健身房). You just follow some habits that thin people have. Keep them, and you'll become thin.
    A. Wake-up
    When you wake up in the morning, sit up slowly without using your hands. With legs straight out, bend(弯曲) forward until you feel sore（酸痛） in your back. It will bum about 10 calories.
    B. Start with soup
    When you have a meal, order a clear soup, and have it before having the main food. In this way, you'll feel fuller, so you'll eat less when the main food comes.
    C. An apple (or more) a day
    Apples are full of fiber and water, so your stomach will want less. The study shows that people who eat at least three apples a day lose weight.
    D. Stand up and walk around
    Every time you use the mobile phone, stand up and walk around. Heavy people sit on average (平均）two and a half hours more each day than thin people. This skill is very important as standing up and walking around will bum 50 0r more calories.
Use these skills, and you will have a big weight loss.

（Ⅰ）请根据表中数据在所给网格中绘制散点图；

（Ⅱ）请根据表中提供的数据，用最小二乘法求出y关于x的线性回归方程 $\widehat{y}=\widehat{b}x+\widehat{a}$ （其中 $\widehat{b}$ 保留2位有效数字）；

（Ⅲ）根据（Ⅱ）中的计算结果，若该蔬菜商店买进土豆40吨，则预计可以销售多少天（计算结果保留整数）？

附： $\widehat{b}=\frac{{{\displaystyle \sum }}_{i=1}^n{x}_i{y}_i-n\overline{x}\overline{y}}{{{\displaystyle \sum }}_{i=1}^n{x}_i^2-n{\overline{x}}^2}$ ， $\widehat{a}=\overline{y}-\widehat{b}\overline{x}$ ．

下列说法中不正确的是（   ）