15. Given the non-intersecting lines a: (x+y=z=2 (x-2y+z=1 and b: (2x-y-z=4 x+y+z=1 a. Find the plane through a parallel with b. b. Find the line through P(1,0,1) that intersect with a and b, and give its parameter equation. c. Find the line that intersects with a and b, and that is parallel to c:x=y-2=3-z. Give the parameter equation of this line.