substitution rate的用法和樣例：
例句
- When there is a diminishing marginal rate substitution, preferences are convex.
邊際替代率是逐漸減少的，偏好就會(huì )凸起。 - The marginal rate of substitution diminishes as we move down along an indifference curve.
當我們向下滑動(dòng)無(wú)差異曲線(xiàn)時(shí)，邊際替代率的減少。
