Suppose:

Data one has data for Subject IDs $1,2,5,6,9,10$ and $15.$

Data two has data for subject IDs $1,2,3,4,5$ and $6.$

Consider the following code:

Data three;

merge one $($in $=$in$1)$ two$($in $=$in$2)$ ;

by subjectid;

if in$1$ and in$2$;

run;

How many subjects will be represented in data three?

Group of answer choices

None

One

Three

Four