“…This together with the boundedness of the state variables and coefficients of the controlled system over the finite interval [0, T ], make it possible to use the existence result presented in theorem 9.2.1 in the book of Lukes to prove this theorem. Hence, the following conditions should be satisfied (see the works of Fister et al and Xu et al for similar arguments): - (1)The set of solutions of the controlled system and u i ∈ Ω, i = 1,2, is not empty;
- (2)The control space Ω is closed and convex;
- (3)The right‐hand side of the controlled system is continuous, bounded, and can be written as a linear function with respect to the controls with coefficients depending on the states;
- (4)The integrand of the objective functional is convex on Ω with respect to u i , i = 1,2, and there exist constants ρ > 1, C 1 > 0, and C 2 such that
Attending to the definition of Ω and the nonnegativity of the state variables, the set of solutions of the controlled system with initial conditions and u i ∈ Ω, i = 1,2, is not empty, which proves the Condition 1. The Condition 2 is satisfied since the control set Ω is closed and convex by definition.…”