Mary bought Wind$-$Gen Electric stock for $$8000\mathrm{.}00.$ After $4$ months, the value of her shares had risen by $$150\mathrm{.}00$ and dividends totaling $$120\mathrm{.}00$ had been paid. $($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 $4$ 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. Conclusion: Mary's return was equivalent to an annual simple interest rate of about $\_\_\%.$