Mercantile Law help needed

Existing goods are goods owned by the selller at the time of sale while those goods which are yet to be owned by him like agricultural products yet to be produced are the examples of future goods.

the goods may be obtained by him depending upon certain contigency which may or may not take place. like if he enters into an agreement to sell 100 kg of good tomatoes possibly to be grown by him and if the tomatoes are later not grown by him then this becomes a contract dependent upon contingency

a contract will be called a contract of sale of goods if the goods are in existence at the time of sale but if the goods are not in existence then any agreement made to sell those goods yet to be manufactured will be called agreement to sell.