For a unique solution case, if $\lambda\neq5 $, is enough, it does not depend on the $\mu.$
for this case $\mu=9$ or $\mu\neq9$ it doesn't matter in case of a unique solution.Because when $\lambda\neq5$,rank of (A)=3 and rank(A:B) is also $3$.
Rank=Maximum Number of independent Rows/Columns.
Rank=Dimension(Order)-Nullity.