A) Find direction numbers for the line of intersection of the planes x + y + z = 7 and x + z = 0. (Give the answers as a comma-separated list.)
B) Consider the following planes x + y + z = 1 , and x + 3 y + 3 z = 1.
Find parametric equations for the line of intersection of the planes. (Use the parameter t.)
C) Consider the following planes x + y + z = 1 , and x + 3 y + 3 z = 1.
Find the angle between the planes. (Round the answer to one decimal place.)