What constant must we place in the box below in order to be able to factor the resulting expression into the product of two linear factors:\( 2mn - 16m - 7n + \boxed{\phantom{00}}\)
2mn - 16m - 7n + ???
2m (n - 8) - 7 (n - 8)
(2m - 7) ( n - 8)
2nm - 16m -7n + 56
+16 
