Dr Objectives: Advancing our understanding of vectors. Using a vector to store class object pointers. Implementing a vector of pointers to achieve polymorphism. Question: Download Lab21_Given.epp. A base class, two derived classes, and a main function is provided. 1. Read and understand the given code. 2. Implement the following functions as described in each TOD0 task: a, void addDoctor(vector?personType., &vec) b. void addLawyer(vector &vec, vectorxpersonType >::iterator &it) d. void clearVec(vector &vec, vectorxpersonType >::iterator &it) d. void clearVec(vector