The minimum number of codewords in a code with t ternary and b binary coordinates and covering radius R is denoted by K(t,b,R). In this paper, necessary and sufficient conditions for K(t,b,R)=M are given for all M = 5. By the help of generalized s-surjective codes, we develop new methods for finding bounds for K(t,b,R). These results are used to prove the equality K(9,0,5)=6 as well as some new lower bounds such as K(2,7,3) =7, K(3,6,3)=8, K(5,3,3)=8, and K(9,0,4)=9. Some bounds for (nonmixed) quaternary codes are also obtained.
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