Answer:
she has 3/4 of the material left or 75%
For compound interest, the formula is given below:
Amount = 
Here, P = 18,800
n = 2
r = 13/100
So, Amount = 

= 18,800 × 1.2769
= 24005.72
Compound Interest = Amount - Principal
Compound Interest = 24005.72 - 18800
= 5205.72
Hence, the compound interest for Rs.18,800, calculated for 2 years at 13% rate of interest compounded annually is Rs.5205.72.
The answer is 4 if I am correct
It should be around 13 percent I am not totally sure