Define sets as follows: J=\{1,2,5,6\}, \quad K=\{3,6,7,8\}, \quad L=\{4,5,7\}, \quad M=\{1,4,6,8\}, \quad N=\{6,\{8\}\} . Find the following sets. \text { (a) } J \cap K \text {. } \text { (c) }(\mathcal{P}(K) \cap N) \times N \text {. }