A cement company has three factories which transport cement to four distribution centres. The daily production of each factory, the demand at each distribution centre, and the associated transportation cost per tonne from factory to distribution centre are given in the Table.

A factory produces \( m \) (i = 1, 2, ..., m) products, each of which requires processing on \( n \) (j = 1, 2, ..., n) workstations. Let \( a_{ij} \) be the amount of processing time that one unit of the \( i^{th} \) product requires on the \( j^{th} \) workstation. Let the revenue from selling one unit of the \( i^{th} \) product be \( r_i \) and \( h_i \) be the holding cost per unit per time period for the \( i^{th} \) product. The planning horizon consists of \( T \) (t = 1, 2, ..., T) time periods. The minimum demand that must be satisfied in time period \( t \) is \( d_{it} \), and the capacity of the \( j^{th} \) workstation in time period \( t \) is \( c_{jt} \). Consider the aggregate planning formulation below, with decision variables \( S_{it} \) (amount of product \( i \) sold in time period \( t \)), \( X_{it} \) (amount of product \( i \) manufactured in time period \( t \)) and \( I_{it} \) (amount of product \( i \) held in inventory at the end of time period \( t \)). \[ \text{max} \sum_{t=1}^{T} \sum_{i=1}^{m} (r_i S_{it} - h_i I_{it}) \] subject to \[ S_{it} \ge d_{it} \forall i, t \] <capacity constraint>
<inventory balance constraint>
\[X_{it}, S_{it}, I_{it} \ge 0; \, I_{i0} = 0 \] The capacity constraints and inventory balance constraints for this formulation are
An electricity utility company charges ₹7 per kWh. If a 40-watt desk light is left on for 10 hours each night for 180 days, what would be the cost of energy consumption? If the desk light is on for 2 more hours each night for the 180 days, what would be the percentage-increase in the cost of energy consumption?