Alinear inequality over variables x1; : : : ; xk is an inequality of the form c1x1 +: : : +ckxk ≤ b, where c1; : : : ; ck and b are integers. given a set of such inequalities, the problem is to decide whether it has an integeral solution, i. e., whether one can assign integeral values to all variables in such a way that all inequalities are satisfied. prove that this problem is np-complete.