Consider a database that has the relation schema CR(StudentName, CourseName).…

Consider a database that has the relation schema CR(StudentName, CourseName). An instance of the schema CR is as given below.

$\begin{array}{|c|c|} \hline \textbf{StudentName} & \textbf {CourseName} \\\hline \text {SA} & \text{CA} \\\hline \text{SA} & \text{CB}\\\hline \text{SA} & \text{CC} \\\hline \text{SB} & \text{CB} \\\hline \text{SB}& \text{CC} \\\hline \text{SC} & \text{CA}\\\hline \text{SC}&\text{CB} \\\hline \text{SC} & \text{CC} \\\hline \text {SD} & \text{CA} \\\hline \text{SD} & \text{CB}\\\hline \text{SD} & \text{CC} \\\hline \text{SD} & \text{CD} \\\hline \text{SE}& \text{CD} \\\hline \text{SE} & \text{CA}\\\hline \text{SE}&\text{CB} \\\hline \text{SF}& \text{CA} \\\hline \text{SF} & \text{CB }\\\hline\text{SF} & \text{CC} \\\hline \end{array}$

The following query is made on the database.

$T1 \leftarrow \pi _{CourseName}\left ( \sigma _{StudentName=SA}\left ( CR \right ) \right )$

$T2 \leftarrow CR\div T1$

The number of rows in $T2$ is ______________ .