The table shows how the average age of first marriage of Japanese women has varied since 1950 .
(a) Use a graphing calculator or computer to model these data with a fourth-degree polynomial.
(b) Use part (a) to find a model for $A^{\prime}(t)$.
(c) Estimate the rate of change of marriage age for women in 1990 .
(d) Graph the data points and the models for $A$ and $A^{\prime}$.