please only do ex4

Exercise 4: A brute force solution to finding a longest common subsequence is to form all possible alignments, and then take the one that has the most matching symbols. This will certainly work, but the algorithm will be slow for the simple reason that the number of alignments grows quickly. How many alignments are there of two strings of length equal to 3? (Hint: it may be easier to instead count the number of alignment paths for these strings.) Exercise 2: Draw the path through the alignment graph corresponding to the following alignment. TCGAC--ATT CC---GAA-T