Outsourcable Tasks

Assume we have two multisets of tasks P and Q. Let these multisets are in sizes of m and n, and assigned to agent A1 and agent A2, respectively and independently. After the task assignments, these agents can cooperate the tasks which is assigned both of them without any additional cost. For example, let our defined tasks set is {M,N,T,U,V,X,Y,Z}, and P={Y,Z,N,U,Y,M}, Q={M,Z,U,Y,V} then cooperated tasks are {Y,Z,U,M}