Hi, I am a 5th class engineer. Now I am pursuing for 4th class but books are costly to save some money I am going to buy used books there is a one person who is selling 4th class 3rd edition both part A and B for 450 dollars but there is no workbook for both part I want to know Is it possible if I do not buy workbook it be will be Ok??moreover, there is only little difference between 3 and 3.5 edition Thanks