To solve this problem, let's first extract the values for $a$, $b$, and $c$ based on the last three digits of the new NIM, which are 1, 5, and 3:

• $a = 1$
• $b = 5$
• $c = 3$

Now, let’s update the frequencies in the table based on these values:

1. For the interval 60-69: $11 + c = 11 + 3 = 14$
2. For the interval 70-79: $9 + b = 9 + 5 = 14$
3. For the interval 80-89: $8 + a = 8 + 1 = 9$

Thus, the updated frequency table is:

Calculations

1. Mean (Rata-rata): $\text{Mean} = \frac{\sum (x \cdot f)}{\sum f}$ where $x$ is the midpoint of each salary range, and $f$ is the frequency.

2. Median: The median is the value at the midpoint of the cumulative frequency distribution.

3. Mode (Modus): The mode is the salary range with the highest frequency.

I can calculate these values for you. Would you like me to proceed with the full calculations for each?