Can some one help me with this algebra problem

For the data below:
year, x ----------------number of ecectically filed tax returns, z (in millions)

1995, 0 ----------------11.807( There are no negative I just used -- to space)
1997, 2 ----------------19.136
1999, 4 ----------------29.349
2001, 6 ----------------40.245
2003, 8 ----------------52.945
2005, 10----------------68.476

a) find a linear model using the years 0 and 4
b) find a linear model using the graphing calculator.
c) what is the correlation coefficient?
d) use your model to predict the numbers for 2010.

a)
m = (y2 - y1) / (x2 - x1) ====> (0 , 11.807) & (4 , 29.349)
m = (29.349 - 11.807) / (2 - 0)
m = (17.542/4) = 4.3855

y - y1 = m * (x -x1) =====> having any points of (0 , 11.807) & (4 , 29.349)
y - 11.807 = 4.3855 * (x -0)
y - 11.807 = 4.3855x
y = 4.3855x + 11.807

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b)

i used excel, which is y = 5.652 * x + 8.731

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c)

correlation:
R^2 = 0.986

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d)

2010 is as 20
y = 4.3855 * 20 + 11.807
y = 99.517 millions