A 4 mm thick aluminum sheet of width \( w = 100 \) mm is rolled in a two-roll mill of roll diameter 200 mm each. The workpiece is lubricated with a mineral oil, which gives a coefficient of friction, \( \mu = 0.1 \). The flow stress (\( \sigma \)) of the material in MPa is \( \sigma = 207 + 414 \varepsilon \), where \( \varepsilon \) is the true strain. Assuming rolling to be a plane strain deformation process, the roll separation force (\( F \)) for maximum permissible draft (thickness reduction) is ________________ kN (round off to the nearest integer).
