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**Comprehension:**

All the first-year students in the computer science (CS) department in a university take both the courses (i) $\mathrm{Al}$ and (ii) $\mathrm{ML}$. Students from other departments (non-CS students) can also take one of these two courses, but not both. Students who fail in a course get an $\mathrm{F}$ grade; others pass and are awarded $\mathrm{A}$ or $\mathrm{B}$ or $\mathrm{C}$ grades depending on their performance. The following are some additional facts about the number of students who took these two courses this year and the grades they obtained.

- The numbers of non-CS students who took $\mathrm{Al}$ and $\mathrm{ML}$ were in the ratio $2: 5$.
- The number of non-CS students who took either $\mathrm{Al}$ or $\mathrm{ML}$ was equal to the number of CS students.
- The numbers of non-CS students who failed in the two courses were the same and their total is equal to the number of CS students who got a $\mathrm{C}$ grade in $\mathrm{ML}$.
- In both the courses, $50 \%$ of the students who passed got a $\mathrm{B}$ grade. But, while the numbers of students who got $\mathrm{A}$ and $\mathrm{C}$ grades were the same for $\mathrm{Al}$, they were in the ratio $3 : 2$ for $\mathrm{ML}$.
- No CS student failed in $\mathrm{Al}$, while no non-CS student got an $\mathrm{A}$ grade in $\mathrm{Al}$.
- The numbers of CS students who got $\mathrm{A, B}$ and $\mathrm{C}$ grades respectively in $\mathrm{Al}$ were in the ratio $3: 5: 2$, while in $\mathrm{ML}$ the ratio was $4: 5: 2$.
- The ratio of the total number of non-CS students failing in one of the two courses to the number of CS students failing in one of the two courses was $3: 1$.
- $30$ students failed in $\mathrm{ML}$.

How many students got $\mathrm{A}$ grade in $\mathrm{Al}$?

- $63$
- $42$
- $84$
- $99$