Answer
selling in November gives the highest annual
return of $ r\approx 58.96\%$
Work Step by Step
With $ INT=FV-PV\quad$ we solve
$INT=PVrt \quad $for r, (divide both sides with $PV\cdot t$)
$r=\displaystyle \frac{FV-PV}{PV\cdot t}$
We build a table based on this formula for each month,
with PV= $235.97$ , and each month being $\displaystyle \frac{1}{12}$ of a year
From the table we see that
selling in November gives the highest annual
return of $ r\approx 58.96\%$
