In this question, you should round answers appropriately where necessary. Between 2010 and 2020, the total number of followers of a popular Twitter account can be modelled by the linear equation: f = 8.6t ? 70 (10 ? t ? 20) where f is the total number of Twitter followers in 100 000's and t is the number of years since the start of 2000.

(a)

(i) Find the modelled number of followers at the start of 2012 to the nearest 10 000.

(ii) Calculate the year in which the total number of followers reaches 7 million.

(iii) Write down the gradient of the straight line represented by the equation f = 8.6t ? 70 (10 ? t ? 20). What does this measure in the practical situation being modelled?

(iv) State the vertical intercept and explain why a negative y-intercept does not represent an issue for the model.

(v) Suggest two ways in which the graph below could be improved.

y 120- 100- 80- 60- 40- 20-1 14 Title A graph showing the number of Twitter followers of a popular account in 100 000's.