coordinate geometry question
The line L passes through the points P ( -1,2) and Q (11,8).
A) Find an equation for L in the form y= mx+c, where m and c are constants.
( I'm fine with this part of the question)
B) The line Z passes through the point R (10,0) and is perpendicular to L. The lines L and Z intersect at the point S.
Calculate the coordinates of S
( to find the coordinates of S you equate the first equation L to the equation of the second line Z and then find the values of x and y I think? Please correct me if I'm wrong)
C) Show that the length of RS is 3 square root 5
(Use formula of finding the length of a straight line)

D) Hence, or otherwise, find the exact area of triangle PQR
This is the part I'm struggling with, please answer if you can
Thanks