$($b$)$ Suppose that vec$(m)*vec(r)=$a and vec$(n)*vec(r)=b$ describe two parallel planes. Derive a formula for the distance between them. Your answer will be in terms of vec$(m),$vec$(n),a,b.$

$d=\frac{|a-b|}{|(vec(m))|}$

$|m|=\sqrt[\phantom{2}]{m_1^2+m_2^2+m_3^2}$

$d=1$