Hey guys. The question goes like this :

Coordinates of A(-1,2,5) and B(2,-2,11). Plane p passes through B and is perpendicular to AB. It is required to find

(a) Equation of plane p

(b) Acute angle between plane p and y axis.

An equation for p is 3x - 4y + 6z = 80

What is the next step to calculate the angle ?

i use the formula cos θ = A . B / |A| x |B| ,

i can substitute the value of A with normal vector of plane p. Then how should i proceed? Is there a direction vector for the y axis ??

Thanks in advance