Mary bought Wind$-$Gen Electric stock for $$8000\mathrm{.}00.$ After $4$ months, the value of her shares had risen by $$160\mathrm{.}00$ and dividends totaling $$120\mathrm{.}00$ had been paid.

$($Round to two decimal places.$)$

$($a$)$ Find the return on investment on this investment $($ROI$).$

$($b$)$Find the simple interest rate she earned on this investment if she sold the stock at the end of the $6$ months.

i$)$ P $=$

ii$)$ I $($interest earned $=$ the total of all gains$)=$

iii$)$ t $($no of year$)=$

iv$)$ Use I $=$ Prt$,$ find r$,$ and Calculate the result in percentages.

v$)$ Conclusion: Mary$$s return was equivalent to an annual simple interest rate of about $\_\_\_\_\_\_\%.$