When a mixed costs exists, which of the following statements is correct. A? When a mixed costs exists, which of the following statements is correct. A? A mixed costs contains both direct and indirect costs. B, You cannot leave a mixed costs as is you have to determine what portion is fixed and what portion is variable. C, A mixed costs changes in total in proportion to the level of activity. D, Most companies do not have mixed costs that they have to deal with Solution B,  You cannot leave a mixed costs as is you have to determine what portion is fixed and what portion is variable. .