“…Very recently, an optimality condition for (1.1) was established in [41] for the case when f t are not necessary lsc, and a Lagrangian duality result via the interiority technique for (1.3) was established in [3] without any continuity assumption on f and g. Indeed, in the mathematical programming, many of the problems naturally involve non-convex and non-continuous functions. For example, in the DC infinite programming (see for example [7,19,20,21,22] and references therein), the objective functions and constraint functions are, in general, assumed to be DC functions (such a function is, by definition, a difference of two convex functions and so can be neither convex nor lsc). Another important example is the convex composite problem which has been studied extensively by many researchers (see [14,39,46,47,52] and references therein).…”