gravitational potential energy is given by formula
[tex]U = mgh[/tex]
here we need to compare the gravitational potential energy of stone 2 with respect to stone 1
so we will say
[tex]\frac{U_2}{U_1} = \frac{m_2gh}{m_1gh}[/tex]
[tex]\frac{U_2}{U_1} =\frac{m_2}{m_1}[/tex]
given that
[tex]m_2 = 4 m_1[/tex]
now we have
[tex]\frac{U_2}{U_1} = 4[/tex]