Answer: The slope parallel to the line is zero. The slope perpendicular to the line is undefined since y=1 has a slope of zero.
Explanation:
For the equation y=1 you would rewrite it as y = 0x +1 and it would just be a straight line that is one up from the x-axis.
Also an easy way to find the slope of a line that is perpendicular is to remember that the slope is the opposite reciprocal, meaning you just flip the slope you have in the original equation so if its 3/1 flip it to 1/3
However, parallel lines are equal to the slope, so basically the slope stays the same.