Two situations are shown in figures $(a)$ and $(b)$. In each case,$m_1 = 3 \ kg$ and $m_2 = 4 \ kg$. If $a_1$ and $a_2$ are the respective accelerations of the blocks in these situations,then the values of $a_1$ and $a_2$ are respectively [ $g = 10 \ ms^{-2}$ ]

• A
  $\frac{20}{7} \ ms^{-2}, \frac{10}{7} \ ms^{-2}$
• B
  $\frac{10}{7} \ ms^{-2}, \frac{25}{7} \ ms^{-2}$
• C
  $\frac{40}{7} \ ms^{-2}, \frac{10}{7} \ ms^{-2}$
• D
  $\frac{30}{7} \ ms^{-2}, \frac{5}{7} \ ms^{-2}$