The upper end of the spring is fixed and a mass $m$ is attached to its lower end. When the mass is slightly pulled down and released,it oscillates with a time period of $3 \text{ s}$. If the mass $m$ is increased by $1 \text{ kg}$,the time period becomes $5 \text{ s}$. The value of $m$ is (mass of the spring is negligible).

• A
  $\frac{3}{8} \text{ kg}$
• B
  $\frac{5}{9} \text{ kg}$
• C
  $\frac{8}{13} \text{ kg}$
• D
  $\frac{9}{16} \text{ kg}$