A homogenous, linearly elastic rod AB is connected to a linearly elastic spring BC in between the fixed supports at A and C, as shown in the figure. The cross-sectional area, modulus of elasticity, and the coefficient of thermal expansion of the rod AB are 500 mm\(^2\), \(60\times10^3\) MPa, and \(12\times10^{-6}\) per \(^{\circ}\)C, respectively. The stiffness (k) of spring BC is 2500 N/mm.
(Figure not to scale)
The internal force (in kN) that will develop in the spring BC when the temperature of rod AB is increased by \(100^{\circ}\)C is
(rounded off to one decimal place).