Assume four stations $51,52,53,$ and $54$ are connected to the same channel, and the multiple access technique used is CDMA. The data from $S1$ is $1,$ from $S2$ is $1,$ from $S3$ is $0$ and from $S4$ is $0.$ The code assigned to the first station $c1=[+1+1+1+1],$ to the second is $c2=[+1+1-1-1],$ to the third is $1+1,$ and to the fourth is $c4=[+1-1+1-1].$

a$.$ Determine the data transmitted through the channel.

b$.$ Demonstrate how $S1$ receives the data, transmitted by $S4$