How to make sure you get a car?

I attended a session and learn a bit about contracts, or specifically a legal contract..

So according to the speaker, to constitute a contract, there shud be 4 elements,

- Offer
- Acceptance

These 2 forms an agreement, then taking a step further,

- Price of agreement

Meaning there shud be some kind of value exchange on the agreement, such as the most commonly used : deposit

and finally, there should be a "legal consequence" to it...

So the speaker gave these example,

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Case 1:
A sales manager promises to give 30% commision to the sales people on every deal they strike. so the sales team went all out and came back with good sales results and the team manager says: "haha, i was just kidding.."

Offer and Acceptance: Every deal with a comm of 30%
Price: Team went out to sell and got results back

can you sue?
answer: yes

Case 2:
Your dad tells you, "son if u study hard and graduate with 1st class honor, i will buy you a car.." and you say okay, and studied real hard and finally graduated with a 1st class honor.
Then on the convocation day, you ask ur dad, "dad, so where's my car?"
and he says, :"Son, now that u hav grad with such good results, u can surely get a good job and buy ur own car.." gives u a pat and walked away..

Offer and Acceptance: Buy a car if grad with 1st class honor
Price: work hard and got it

can you sue?
answer: no - reason: when he says it, neither expect any legal consequnce to it..

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Sometimes, these things are kinda interesting to know...

and the lesson learned: you shud always remember to say this when ur dad promises something, "dad, i will sue u if u dun do it" then it completes the requirement!