addition solid solution

例句：

1. 1.The cost of the new product is an addition to our budget.
   新产品的成本是我们预算的一个额外部分。
2. 2.The teacher added a new unit on calculus to the lesson plan.
   老师在课程计划中增加了一个关于微积分的新单元。
3. 3. The company's profits have been adding steadily since its inception.
   自公司成立以来，利润一直在稳步增长。