How do you plan to solve it?
module concat8_packer(A,B,C,D,OUT); input [3:0] A; input [1:0] B; input C; input D; output [7:0] OUT; assign OUT[7:4]=A[3:0]; assign OUT[3:2]=B[1:0]; assign OUT[1]= ~C; assign OUT[0]=D; endmodule