The total amount withdrawn by Mohan during the year = ₹80,000
The rate of interest to be charged on drawings = 12% per annum
Unless specified otherwise, it is assumed that drawings are made evenly throughout the year.
When drawings are made evenly, interest is charged for an average period of 6 months.
Now, using the formula:
Interest on Drawings = Amount $\times$ Rate $\times$ Time
$\Rightarrow$ Interest = 80,000 $\times$ $\dfrac{12}{100}$ $\times$ $\dfrac{6}{12}$
$\Rightarrow$ Interest = 80,000 $\times$ 0.12 $\times$ 0.5
$\Rightarrow$ Interest = ₹4,800
Thus, interest of ₹4,800 will be charged from Mohan for his drawings.