Answer:
infinite or undefined
Explanation:
Use the slope equation:

Use the 2 points:
(0,6) and (0,5)
Substitute in the values:

simplify

Since we are left with a fraction over 0, we can say that the slope is infinite or undefined, since the fraction is not possible. If we were to graph these 2 points and draw a line through them, the points would both end up on the y-axis, creating a vertical line. A vertical line's slope is infinite or undefined.
Hope this helps! :)