The population of a town is 8000. It decreases annually at the rate of 20% p.a. What will be its population after 2 years? Choose the correct choice from the following answers
A) 4300 B) 4500 C) 5120 D) 5230 E) 5366

Rationale: "formula : ( after = 100 denominator ago = 100 numerator ) 8000 × 80 / 100 × 80 / 100 = 5120 c"
Answer: C