An uninitiated student once visited a test prep portal www. Lamamla. in to assess her quantitative ability for SSC CGL. She took a test in which there were total 18 problems each with four option-A, B, C and D. After glancing through the whole test paper she realized that she was not able to crack even a single problems. Then after a while she changed the answers by marking B in each third problem, starting with the third problem. Unsatisfied with her answer, she again changed the answer by marking C in each second problem, starting with the second problem. In her final attempt to guess the answer,she changed the answers by marking D in each ninth problem, starting with the ninth problem. While.changing the answer she moves from the first to the last problem in an orderly way. What are the number of final answer that she marked in terms of A, B, C, and D, respectively?