Consumer prices the data in the table can be modeled by the function
C(x) = 20.000783x3 + 0.124x2 - 1.74x + 25.2
where x = 0 represents 1945 and c(x) is the consumer price index (CPI) in year 1945 + x. During what year does the model predict that the rate of change of the CPI reached its maximum?