a) The surface area of a right rectangular prism is given by the formula `2lw + 2lh + 2wh`, where `l`, `w`, and `h` are the length, width, and height of the prism respectively. Plugging in the values for this prism, we get `2(15)(6) + 2(15)(10) + 2(6)(10) = 180 + 300 + 120 = 600`. So the surface area of this right rectangular prism is **600 m²**.
b) Marcelo has a total of `3 + 1 + 6 + 2 = 12` marbles in his bag. The fractional part of the bag that is red is `3/12` which can be simplified to **1/4**.
