The president of State University wants to forecast student enrollments for this academic year based on the following historical data:

?

Year Enrollments

$5$ ?Years ago $15,000$

$4$ ?Years ago $16,000$

$3$ ?Years ago $18,000$

$2$ ?Years ago $20,000$

Last Year $21,000$ ?

What is the forecast for this year using the least squares trend line for these data?