Correct Answer - Option 1 : 630.5

**Given:**

A sum becomes Rs.6888 in 8 years and becomes Rs.7380 in 10 years.

**Formula:**

Amount under simple interest = P × r × t/100

Amount under compound interest = P + (P × r × t/100)

where, P is principal, r is rate of interest and t is time.

**Calculation:**

Interest = 7380 - 6888 = 246

P = 6888 – 1968 = 4920

R = 246 × 100/4920 = 5%

In compound interest,

4000 × 21 × 21 × 21/(20×20×20) = 4630.5

∴ Compound interest earned = 630.5