We came into the kitchen and found that the cake had been eaten by a cat. This could be any cat, if you want to say that the cake was eaten by a cat you mentioned before: We came into the kitchen and found that the cake had been eaten by the cat. I would personally say: We went into the kitchen and found that the cake had been eaten by a (or the) cat. I left out "out" from all these sentences, I didn't notice because leaving it out is more natural. It is not wrong if left in.

A formal Letter

Could you correct me, please?

Dear Director John

I am writing with regard to your project mentioned “The OLPC” which is offering laptops to our children. This is a good idea for developing countries but it is not so good for the Third World.

I believe that this might not be a large benefit to the Third World because of the problem of the lack of internet connection. Also, the Third World is more concerned about food, so I personally feel that it is most important is to give food.

In conclusion, I recommend that your project should focus on developed countries; however, poor children would still love help.