In this article, we consider the maximum cocliques of the 2 11 :M 24 -graph K. We show that the maximum cocliques of size 24 of K can be obtained from two Hadamard matrices of size 24, and that there are exactly two maximum cocliques up to equivalence. We verify that the two nonisomorphic designs with parameters 5-(24,9,6) can be constructed from the maximum cocliques of K, and that these designs are isomorphic to the support designs of minimum weights of the ternary extended quadratic residue and Pless symmetry [24,12,9] codes. Further, we give a new construction of K from these 5-(24,9,6) designs. q