Angle rst if angle tsu=46.7° and angle rsu =83.5°

Well, there are 13 places that each horse can place. That means the first place has 13 options, second place has 12 options, third place has 11 options, etc. Though, we only care up to fourth place. When doing probability, we're multiplying in this case. So, here's the process:

How many ways all the horses can place = 13! = 6227020800
How many ways the first four places can place = 13*12*11*10 = 17160

Divide the second by the first and multiply by 100 for the probability as a percent:

(17160/6227020800)*100% ≈ 0.00027557319%