Help on number 3? Thank you

Find the area of the shaded region.

In 2014, the three largest economies in the world were (listed in order, from largest): a) the u.s., china, germany. b) the u.s., china, japan. c) china, the u.s., japan. d) china, the u.s., germany.

Write a linear funtion f with the values f(2)=-1, and f(5)=4