杜克官网:
Master's students are required to enroll in and pay tuition for at least three semesters of full-time study. After that, they will be charged at an estimated rate of $2,990 per credit. Master's summer tuition will be charged at the per-credit rate up to a maximum of one-half the fall/spring full-time tuition.
上述这一段话的意思似乎是说前三个学期的学费是固定为$25,740。只有最后一个学期和夏季学期的收费是按照学分来的。
出处:https://gradschool.duke.edu/financial-support/cost-attend#masters
另外Tufts似乎并非按照学分收费。
The one-year residency requirement means that the student is obligated to pay full tuition for two semesters unless a portion of tuition is waived through a tuition scholarship.
对于Mres:
In order to receive the Master of Science Research-Based degree, a student must complete a two-year residency requirement and must pass twelve semester courses.。
出处:https://ase.tufts.edu/economics/grad/
这两段话所指的residency requirement的意义应该相同。
Tufts应该不是按照学分收费的。
Tufts一年学费$49,892。
出处:https://asegrad.tufts.edu/tuition-and-financial-aid
楼主的估算方法存在一定的改进空间。