Implementing change suggested in #435 (#436)

Co-authored-by: Drew Lewis <30658947+siwelwerd@users.noreply.github.com>

source/precalculus/exercises/outcomes/LF/LF4/generator.sage

@@ -41,9 +41,9 @@ class Generator(BaseGenerator):
       point5=(point5[0],point5[1]+choice([-4..-1,1..4]))
 
     slope = -1*line.lhs().coefficients(x)[1][0]/line.lhs().coefficients(y)[1][0]
-    if orientation1=="parallel":
+    if orientation2=="parallel":
       slope2=slope
-    elif orientation1=="perpendicular":
+    elif orientation2=="perpendicular":
       slope2=-1/slope
     new_line = y-point5[1]==(x-point5[0]).mul(slope2,hold=True)