The reaction time of a particular chemical changes with temperature. An experiment to observe the effect of temperature(in degree Celsius, C) on the reaction time(in seconds) of the chemical is conducted. The following results are obtained. At each temperature, the experiment was repeated twice using the same amount of chemical.

Temperature, x Reaction Time, y 10 59 52 

 20 51 38 

 25 43 59 

 30 50 39 

 35 42 29 

 40 40 53 

 50 45 52 

 60 49 34 

a). Using the R software or otherwise, plot a scatter diagram for these data. Describe the plot in terms of the relationship between temperature and reaction time of the chemical.

b). Find the least squares regression equation of the reaction time of the chemical on temperature. Interpret the coefficients of the equation obtained.

c). Compute the coefficient of determination and explain what the value means.

d). Is it reasonable to use the equation in part(b) to predict the reaction time of the same amount of chemical at 75 C ? Justify your answer.