A teacher gives her Spanish students a test each week. Some of the students' marks for two weeks are shown in the scatter diagram. 401 35- 30- 25- Mark in week 2 20- 15- 10- 5- x 10 15 20 25 30 35 40 Mark in week 1 (a) Leo scored 28 marks in week 1 and 30 marks in week 2. On the scatter diagram, plot a point to show Leo's marks. (b) On the scatter diagram, draw a line of best fit. (c) Sonia scored 20 marks in week 1 but was absent in week 2. Use your line of best fit to estimate a mark for Sonia in week 2.