For a $2 \times 2$ square matrix $X = \left( \begin{array} { l l } a & b \\ c & d \end{array} \right)$,
$$D ( X ) = a d - b c$$
is defined. For a $2 \times 2$ square matrix $A = \left( \begin{array} { l l } 1 & 1 \\ 0 & p \end{array} \right)$,
$$D \left( A ^ { 2 } \right) = D ( 5 A )$$
Find the sum of all constants $p$ that satisfy this condition. [4 points]