The following data resulted from an experiment to assess the potential of unburnt colliery spoil as a medium for plant growth. The variables are x = acid extractable cations and y = exchangeable acidity/total cation exchange capacity ("Exchangeable Acidity in Unburnt Colliery Spoil," Nature, 1969: 161):
Standardizing the independent variable x to obtain 
and fitting the regression function
yielded the accompanying computer output.
a. Estimate µY.50.
b. Compute the value of the coefficient of multiple determination.
c. What is the estimated regression function 
using the unstandardized variable x?
d. What is the estimated standard deviation of ß2 computed in part (c)?
e. Carry out a test using the standardized estimates to decide whether the quadratic term should be retained in the model. Repeat using the unstandardized estimates. Do your conclusions differ?