In this paper we consider problems of the following type: Let E = { e 1 , e 2 ,..., e n } be a finite set and $${\mathcal {F}}$$ be a family of subsets of E. For each element e i in E, c i is a given capacity and $${\mathcal {w}}$$ i is the cost of increasing capacity c i by one unit. It is...

In this paper we consider problems of the following type: Let E = { e <Subscript>1</Subscript>, e <Subscript>2</Subscript>,..., e <Subscript> n </Subscript> } be a finite set and <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$${\mathcal {F}}$$</EquationSource> </InlineEquation> be a family of subsets of E. For each element e <Subscript> i </Subscript> in E, c <Subscript> i </Subscript> is a given capacity and <InlineEquation ID="IEq7"> <EquationSource Format="TEX">$${\mathcal {w}}$$</EquationSource> </InlineEquation> <Subscript> i </Subscript> is the cost of increasing capacity c <Subscript> i </Subscript> by one...</subscript></subscript></equationsource></inlineequation></subscript></subscript></equationsource></inlineequation></subscript></subscript></subscript>