Y. Sadewa, Y. Afrinkus, B. . Magdalena, Luna Selciella, and Shella Halim, “Analysis of Production Cost Efficiency of Coffee Shop Business ‘Prestasi Kopi’ at Medan State University Based on Linear Equation System and Inverse Matrix in Marginal Cost Analysis, Marginal Revenue, and BEP”, OJES, vol. 5, no. 2, pp. 157–168, May 2026, doi: 10.61730/8xwy8y74.