Answer
We can see a sketch of the derivative function $M'(t)$ below the function $M(t)$
The derivative was negative between the years 1963 and 1971.
Work Step by Step
We can see a sketch of the derivative function $M'(t)$ below the function $M(t)$
The derivative was negative between the years 1963 and 1971. During these years, the graph of the derivative is below the horizontal axis.