Compare the the planes below to the plane $5 x+ 2 y+ z = 4$. Match the letter corresponding to the words parallel, orthogonal, or "neither" which describes the relation of the two planes.

1. $15 x+ 6 y+ 3 z = 3$
2. $5 x+ 3 y+ z = 1$
3. $-2 x+ 5 y = -1$

A. orthogonal
B. neither
C. parallel

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