Let's break down the problem step by step.

First, let's find out how much work each person does per day:

• Mujahid can do 1/8 of the work per day.
• Asad can do 1/12 of the work per day.
• Mithun can do 1/16 of the work per day.

When Mujahid and Asad work together, they can complete: of the work per day.

Now, let's find out how much work they completed together before Asad left. Let's say they worked together for days:

Since Mujahid and Asad together completed a portion of the work before Asad left, the remaining portion of the work is:

After Asad left, Mujahid and Mithun worked together to complete the remaining portion of the work in 2 days. Their combined rate is:

So, the amount of work they completed in 2 days is:

Now, we know that the total work completed after Asad left is equal to the work completed by Mujahid and Mithun in 2 days, which is .

So, we have:

Solving for :

So, Mujahid and Asad worked together for 3 days before Asad left. Therefore, the total time taken to complete the work is .

So, the answer is option: b) 5 days