Periodic Phenomena

The function $f$ is periodic with period $8$. On $0\le x\le 8$, the graph of $f$ is made of line segments joining $(0,-1)$, $(2,3)$, $(3,3)$, $(6,-3)$, and $(8,-1)$. What is the average rate of change of $f$ over the interval $42\le x\le 46$?