You need to identify what the aims and objectives are (presumably these are stated in the question or case study) and then identify who the individual stakeholders of the RSPCA are and how they would want to influence these. For example, one of the stakeholder groups would be the local community who might be interested in influencing any plans for expansion as this could have an effect on their house prices or general well being due to noise from a kennel.
I'm afraid without further detail from the question, it's difficult to be any more specific, but hope this has given you an idea of how to tackle the question.
The customers want the cheapest and best deals they can.
The employees want a stable work environment and good wages to help them in their personal lives.
The suppliers want some one who they can sell their goods to, on a regular basis, and in turn the supplies pay others who work for them.
The owners want to make a profit, so they have money to spend.
The government want the taxes collected by Tesco, and also the social responsibility of having people employed, rather than having to pay the unemployment.
Each one of these stakeholders have influence o the Tesco.
It all helps the economy go round.