$A$ block $A$ of mass $m_1$ rests on a horizontal table. $A$ light string connected to it passes over a frictionless pulley at the edge of the table,and from its other end,another block $B$ of mass $m_2$ is suspended. The coefficient of kinetic friction between the block $A$ and the table is $\mu_k$. When the block $A$ is sliding on the table,the tension in the string is:

• A
  $\frac{m_1 m_2 (1 + \mu_k) g}{m_1 + m_2}$
• B
  $\frac{m_1 m_2 (1 - \mu_k) g}{m_1 + m_2}$
• C
  $\frac{(m_2 + \mu_k m_1) g}{m_1 + m_2}$
• D
  $\frac{(m_2 - \mu_k m_1) g}{m_1 + m_2}$