Answer : Option D

Explanation :

Let P = Rs.100
Simple Interest = Rs. 80 ( ∵ 80% increase is due to the simple interest)
$MF#%\text{Rate of interest} =\dfrac{100 \times \text{SI}}{\text{PT}} = \dfrac{100 \times 80}{100 \times 8} = 10\%\text{ per annum}$MF#%
Now let's find out the compound interest of Rs. 14,000 after 3 years at 10%
P = Rs.14000
T = 3 years
R = 10%
$MF#%\text{Amount after 3 years } = \text{P}\left(1 + \dfrac{\text{R}}{100}\right)^\text{T} = 14000\left(1 + \dfrac{10}{100}\right)^3 \\\\ = 14000\left(\dfrac{110}{100}\right)^3 = 14000\left(\dfrac{11}{10}\right)^3 = 14 \times 11^3 = 18634$MF#%
Compound Interest = Rs.18634 - Rs.14000 = Rs.4634