Perinatal HIV infection: The following table shows the number H of cases of perinatal HIV infections in the U.S. as reported by the Centers for Disease Control and Prevention. Here t denotes years...

Perinatal HIV infection: The following table shows the number H of cases of perinatal HIV infections in the U.S. as reported by the Centers for Disease Control and Prevention. Here t denotes years since 1985.

a. Make a plot of the data.

b. Use regression to find a quadratic model for H as a function of t.

c. Add the plot of the quadratic model to the data plot in part a.

d. When does the model show a maximum number of cases of perinatal HIV infection?