That is an absolutely fascinating question. However, it cannot be answered with the given information. You would need to specify how many segments to the spinner and what the value of each of the segments are.
Here's why:
Let's say that you have a spinner where ALL of the segments have a value less than 200. It would be impossible to get a two-spin total in excess of 400, hence the probability that the sum is at most 400 is 100%, or certainty.
On the other hand, if all of the segments had a value greater than 200, you would be certain to have a sum on two spins greater than 400 and the probability of the sum being at most 400 is zero.
Or it could be anywhere in between those two extremes, depending on the exact configuration of your spinner wheel.
