I guess your essay is in paragraphs.So, first paragraph should be introductory like what the product is, how old it is , from where it is derived and then the next paragraph will consist of benefits and features of the product, after that the paragraph will be of implementation of features in new product. Last paragraph will be conclusion. This will easily make 400 or more words.
I think you can get more idea from this example.Let's say your Product is a toothpaste.So, the starting will be like this -
First Paragraph :Toothpaste name, colour, its fragrance, ingredients included, company's name or how old the company is? or since when people are using it.
Second Paragraph : Features of toothpaste, like how it is different from others, what special quality it has so that it should be used by people, why people should prefer it and not others.
Third Paragraph : what do you think if these features or ingredients are added to the new toothpaste then how it will be useful. For e.g: existing toothpaste consists natural herbs , new one has a chocolate flavored taste; so how do you think the combination of chocolate and natural herbs will make a toothpaste. What will be its uses and why should it be preferred by the people.
fourth Paragraph: (I guess after writing all of the above, this will be your last one i.e. Conclusion) So,here you can mention what you felt about the product. say you can write like this : " my existing product (here, toothpaste) has enormous features that are useful as well as helpful. (Explain any one feature that you like the most).If these features are implemented in the new product, then we can give better combination to the market.
Like this, you can complete answer to your essay question. It's good if you can add some proverbs or anything catchy like that and relevant to your product which draws the attention of the examiner thus providing you good marks.
Hope this helps. Any doubts or questions are most welcomed.