There are a baker 's dozen recognized breeds and several'unofficial ones ' .

有 面包 十几公认的品种和几个'非官方的'。

He bought a baker 's dozen of biscuits .

他买 了 十三块 饼干。

So here 's a baker 's dozen of the most common and most costly mistakes students make in picking a major ( and our best advice on how to avoid them )

所以，这里学生在选择专业时所犯的最常见、代价最重的错误（我们还会拿出自己最好的建议来避免 犯错）。