Let the point \( A \) divide the line segment joining the points \( P(-1,-1,2) \) and \( Q(5,5,10) \) internally in the ratio \( r:1 \, (r>0) \). If \( O \) is the origin and \( {\overrightarrow {OQ} \cdot \overrightarrow{OA}} - \frac{1}{5} \left|\overrightarrow{ OP} \times \overrightarrow{ OA} \right|^{2} = 10 \), then the value of \( r \) is:
