Credit ratings are critically important to firms as they determine, to a large extent, the firm's costs of borrowing funds. Ratings services most commonly followed are Moody's Investment Services and Standard and Poor's. How do they establish the rating? Select one: a. release a detailed document of categories and grades assigned to each thoroughly objective component b. assign grades based on past performance C. assign grades on objective evaluation of past performance and subjective evaluation of firms management d. assign grades based on subjective evaluation of firms management and subjective evaluation of firms past performance