Why did you need to calculate leaf surface area to determine the rates) of transpiration?

Rate of transpiration is dependent on leaf surface area

Explanation:

Leaf has openings called stomata, which is the structure that allows for transpiration to occur, and they are found in the lower epidermis of leaves. Water escapes through stomata. Smaller leaves tend to have large surface area as they have higher number of stomata compared to larger leaves. Large surface area in smaller leaves would result in relative high rates of transpiration when compared to larger leaves having small surface area.

it's diluted or concentrated

in a diluted solution, you can add a lot more solute but in concentrated only a little more can be added