A balloon rises from rest with a constant acceleration \( \dfrac{g}{8} \). A stone is released from it when it has risen to height \( h \). The time taken by the stone to reach the ground is:
\( 4\sqrt{\dfrac{h}{g}} \)
\( 2\sqrt{\dfrac{h}{g}} \)
\( \sqrt{\dfrac{2h}{g}} \)
\( \sqrt{\dfrac{g}{h}} \)