Universal Electric, Inc., manufactures and sells two models of lamps, L₁ and L₂ , the profit being $150 and $100, respectively. The process involves two workers W₁ and W₂ who are available for this kind of work 100 and 80 hours per month, respectively. W₁ assembles L₁ in 20 min and L₂ in 30 min. W₂ paints L₁ in 20 min and L₂ in 10 min. Assuming that all lamps made can be sold without difficulty, determine production figures that maximize the profit.