\displaystyle V_0 = (10 + 5V_0)\times \dfrac{10}{10+6} \times 4,\quadV_0 = -\dfrac{50}{23}\ (\text{V})
\displaystyle V_{10\Omega} = (10 + 5V_0)\times \dfrac{3}{8} \times 10 = -\dfrac{75}{23}\ (\text{V}),\quadP_{10\Omega} = \dfrac{V_{10\Omega}^2}{10} = 1.06(\text{W})