Maybe I'm thinking more with respect to negligence. You can't say "I'm too stupid to live up to the reasonable person standard" or "I tried my best." That is never considered a defense.
I feel pretty strongly that the guy that set the trap would surely by found liable for battery. First of all, it does not matter if he did not specifically target anyone, if he intended the consequences of his actions.. no matter on who. It does not matter if it is possible that someone may not fall, it is important what his intent was. In fact, it does not really matter, now that I think about it, whether he was subst. certainty. In truth, he had a DESIRE to bring about a harmful or offensive contact with someone, i.e. he desired the consequences to result from his actions. To draw anything else fromt he purpose of him digging a hole in the ground and covering it up would be pretty difficult and likely fail in court.
Also, I do not see negligence here. This was carried out with an intent to "see if anyone would fall". This is quite different from, oops I dug this hole and forgot about it, I used it as a garbage can while camping. That would be negligence. Here he clearly intended the result of his actions, the absolute meaning of an intentional tort.
Expectation is easiest. It is the benefit of the bargain. Assumes contract not breached so Helen's profit + costs= $4,000+$15,000 = $19,000 Assuming she does not keep horse = $17,000 (She nets $4,000 which is the benefit of the bargain)
Reliance puts Promissee (Helen) in same position before contract breached (only damages to correct breach) = $15,000-$5,000-$2,000 = $8,000
Restitution puts Promisor (Troy) back in same position before contract breached. In this case the $5,000 goes back to Troy, $15,000 to Helen so the net damages awarded are $10,000.
Expectation $19,000 / $17,000 if salvages horse
Reliance $8,000 (horse is salvaged)
Restitution $10,000 / $8,000 if salvages horrse
Thanks to all who answered so far. Please keep them coming. The larger the sample the better the idea new students can get. Thanks again.