(Euclid 2023, Question 4, CEMC - UWaterloo)

(a) Liang and Edmundo paint at different but constant rates. Liang can paint a room in $3$ hours if she works alone. Edmundo can paint the same room in $4$ hours if he works alone. Liang works alone for $2$ hours and then stops. Edmundo finishes painting the room. How many minutes will Edmundo need to finish painting the room?
(b) On January $1$, $2021$, an investment had a value of $\$400$.
From January $1$, $2021$ to January $1$, $2022$, the value of the investment increased by $A\%$ from its value on January $1$, $2021$ for some $A > 0$.
From January $1$, $2022$ to January $1$, $2023$, the value of the investment decreased by $A\%$ from its value on January $1$, $2022$.
On January $1$, $2023$, the value of the investment was $\$391$.
Determine all possible values of $A$.

Answer Submission Note(s)
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