Problem 3. Complete the following function that replaces each element of a vector V with two copies of the element: void duplicate (vector<__> &V) vector C = V; V.clear (); while (C.size) 0) V.push_back (C[___l); V.push_back (CI__]); C.erase (0); For instance, the following tests should pass: "cat", "bird"); vector V("dog", duplicate (V); test(v.size() == 6); test (V [0] "dog" ) ; test(V[1]dog"); test(V[2]cat"); test(V[3] -- "cat"); test(V[4] -- ''bird'' ); test(V[5] -- "bird'' ); Let n be the length of V. The running time of duplicate is: ?6(1) 6(n) ?6(?)