Believe it or not computers or more correctly processing units (PUs) are becoming part of things we use in everyday life. For example in modern automobiles, a PU may control the braking system, and another may control fuel injection. Similarly, hundreds of PU may work together to make a plane fly. Consider a specific system SYS.SYS has n identical PUs that are connected in a communication network. It takes cooperation of exactly k PUs to perform an operation of size k. However, two Pus can cooperate only if they are directly connected in the communication network. The SYS would like to figure out the largest operation it can perform. Prove that SYS has an NP-complete problem in his bag. To help SYS you can assume that 3SAT is NP-complete.