Final answer:
The total length of the outline of the mini-tennis court that needs to be painted is 36 feet.
Step-by-step explanation:
To find the total length of the outline of the mini-tennis court, we need to calculate the distance between each pair of consecutive vertices and add them up.
Distance between (-2.5,2.5) and (-2.5,0.5) = 2 units * 3 feet = 6 feet
Distance between (-2.5,0.5) and (1.5,0.5) = 4 units * 3 feet = 12 feet
Distance between (1.5,0.5) and (1.5,2.5) = 2 units * 3 feet = 6 feet
Distance between (1.5,2.5) and (-2.5,2.5) = 4 units * 3 feet = 12 feet
Total length of the outline = 6 feet + 12 feet + 6 feet + 12 feet = 36 feet
Therefore, the correct answer is a) 36 feet.