Answer:
The overall score is 75.6
Letter grade is C
Step-by-step explanation:
The question has missing details (See comment section for complete question).
From the complete question, we have:
<u>Proportion:</u>
![Midterm = 15\%](https://tex.z-dn.net/?f=Midterm%20%3D%2015%5C%25)
![Project = 25\%](https://tex.z-dn.net/?f=Project%20%3D%2025%5C%25)
![Assignment = 40\%](https://tex.z-dn.net/?f=Assignment%20%3D%2040%5C%25)
![Exam = 20\%](https://tex.z-dn.net/?f=Exam%20%3D%2020%5C%25)
Scores
![Midterm = 66](https://tex.z-dn.net/?f=Midterm%20%3D%2066)
![Project = 90](https://tex.z-dn.net/?f=Project%20%3D%2090)
![Assignment = 75](https://tex.z-dn.net/?f=Assignment%20%3D%2075)
![Exam = 66](https://tex.z-dn.net/?f=Exam%20%3D%2066)
Solving (a): The overall score
To do this, we simply calculate the mean of the given data.
The mean is calculated by multiplying each proportion by the scores..
So, we have:
![Overall = 15\% * 66 + 25\% * 90 + 40\% * 75 + 20\% * 66](https://tex.z-dn.net/?f=Overall%20%3D%2015%5C%25%20%2A%2066%20%2B%2025%5C%25%20%2A%2090%20%2B%2040%5C%25%20%2A%2075%20%2B%2020%5C%25%20%2A%2066)
![Overall = 9.9 + 22.5 + 30 + 13.2](https://tex.z-dn.net/?f=Overall%20%3D%209.9%20%2B%2022.5%20%2B%2030%20%2B%2013.2)
![Overall = 75.6](https://tex.z-dn.net/?f=Overall%20%3D%2075.6)
Solving (b): The letter grade
From the question, we have:
![A: Mean \ge 90](https://tex.z-dn.net/?f=A%3A%20Mean%20%5Cge%2090)
![B: 80 \le Mean < 90](https://tex.z-dn.net/?f=B%3A%2080%20%5Cle%20Mean%20%3C%2090)
![C: 70 \le Mean < 80](https://tex.z-dn.net/?f=C%3A%2070%20%5Cle%20Mean%20%3C%2080)
The overall score falls in the following category:
![C: 70 \le Mean < 80](https://tex.z-dn.net/?f=C%3A%2070%20%5Cle%20Mean%20%3C%2080)
Because:
![70 \le 75.6 < 80](https://tex.z-dn.net/?f=70%20%5Cle%2075.6%20%3C%2080)
<em>Hence, the letter grade is C</em>