The original graph is given below
a. If the starting number of players is 600 instead of 400 then
The y-intercept will be 600
The new graph will be a vertical stretch of the original graph by a scale factor of 600/400
Therefore,
The y-intercept will be 600. The new graph will be a vertical stretch of the original graph by a scale factor of 1.5
b. If the starting number of players is 800 instead of 400 then
The y-intercept will be 800
The new graph will be a vertical stretch of the original graph by a scale factor of 800/400
Therefore,
The y-intercept will be 800. The new graph will be a vertical stretch of the original graph by a scale factor of 2