The bankers discount and the true discount of a sum at 10% per annum simple interest for the same time are Rs. 100 and Rs. 80 respectively. What is the sum and the time?

• Sum = Rs. 400 and Time = 5 years
• Sum = Rs. 200 and Time = 2.5 years
• Sum = Rs. 400 and Time = 2.5 years
• Sum = Rs. 200 and Time = 5 years