A classic NP-complete problem is called SAT and can be stated as:
Given a Boolean expression can it be made True by some assignment of True or False to each
of its variables?
4.1. If $B(P_0, P_1, \dots, P_{n-1})$ is a Boolean expression in $n$ Boolean variables. Describe the brute-force, worst
case time complexity for showing B is satisfiable or unsatisfiable?
4.2. If B is satisfiable, show that there is a certificate that proves it to be, that is explain.