Two blocks, with masses $m_{1}=4.6 \mathrm{~kg}$ and $m_{2}=3.8 \mathrm{~kg}$, are connected by a light spring on a horizontal frictionless table. At a certain instant, when $m_{2}$ has an acceleration $a_{2}=$ $2.6 \mathrm{~m} / \mathrm{s}^{2},(a)$ what is the force on $m_{2}$ and $(b)$ what is the acceleration of $m_{1}$ ?