Graphing the IPCC Carbon Dioxide Predictions

This graph, from the IPCC 1.5°C report, shows how the rate of carbon dioxide emissions varies with time in two scenarios in which global carbon dioxide emissions decline to reach net zero in 2040 or 2055. For the purposes of this question, only focus on the blue line reaching zero in 2040.

Graphing the IPCC Carbon Dioxide Predictions

a) After 2020, the graph becomes linear. The linear section of the graph passes through the points (2020, y) and (2040, 0). The amount of carbon dioxide released into the atmosphere during these years is 4.2×1014 kg. Find the value of y. Leave your answer in standard form. 
[3 marks]

b) Find the equation of the linear section of the line in the form y=mx+c.
[3 marks]

c) Write down an equation of a line which is parallel to this line.
[1 mark]