Doc,

....and the other 6 horses in the race all have 100% place S/Rates [extreme example]. What chance then for A,B,C,D ? You must work out the win% chance for these 4 hourses to work out the probability for the quin. scenario you mention, otherwise your stuffed and guessing. Place SR is useless mathamaticaly for 4 [only] horses in a 10 horse race.