2000018405

Assuming that $$\left|\begin{array}{ccc}1& a& 5\\ 1& b& 6\\ 1& c& 7\end{array}\right|=-4$$ compute the following determinant: $$\left|\begin{array}{ccc}a& -2& 6\\ b& -2& 7\\ c& -2& 8\end{array}\right|$$