The social grade table shows the different classes in society and how you fit into each one. Rap music and hip hip would attract the audience of people in E, and D. This is because this the style of music is more likely so suit the younger genearation. This age group fits into E as they still rely on the state because they dont work. Also the working class because these are also more likely to be younger people as they dont have proper jobs but just do small bits of work.
Now we know what social grade the magazines audience will be we can work out the price of the magazine, it cant be too expensive so maybe around £1.50 - £2.00 as they people in social grades D and E dont have jobs or highly paid jobs so wont be wanting to spend too much on a magazine, you could also put free stuff in the magazine to get people to buy itm, if they think they are getting something free it will entice them to buy it.
The features in the magazine need to be suited to the audience so not going into details about work and sophisticated living as this is the lifestyle of the middle classes and wouldnt engage with the reader.