There are 4 alternative forms of institutional advertisements being;
Competitive - These types of adverts aim to show that the product presented is better than that of the competitor by showcasing its benefits and features.
Reminder - As the term implies, this advertisement is meant to remind you. Remind you of the product being offered and how it has been beneficial to you.
Pioneering - This is for products that are just starting out and need to be introduced to inform the market of its existence.
Advocacy - These focus on telling the audience the position a company has on an issue.
These are the four alternative forms of institutional advertisements and Public Service is not one of them.
The answer and procedures of the exercise are attached in the following archives.
Explanation
You will find the procedures, formulas or necessary explanations in the archive attached below. If you have any question ask and I will aclare your doubts kindly.