Please help in the context of C++ programming

a) Both the vector container and the list container (a doubly-linked list) have a push_back function which appends an element to the end of the contained sequence of elements. Assume that both containers already contain the integers: 1,2 and 3 . Draw the "beforepicture" of what each container looks like before a fourth element (the element 4) is added through push_back, and an "after-picture" showing what they look like after the element has been added via push_back. (4 marks) b) How would you expect these two different containers to compare in terms of time efficiency when using push_back? (4 marks) c) A vector container is said to offer random access to its elements. Explain what the term random access means and why this is possible with a vector