For their birthdays, Vivaan and Saanvi, who are brother and sister, each received 25 iTunes music downloads and 10 movie passes. Vivaan’s marginal rate of substitution of music downloads for movie passes is 1/4, while Saanvi’s marginal rate of substitution of music downloads for movie passes is 2. For a Pareto improvement over the original allocation, Vivaan gives Saanvi _____ music download(s) for _____ of her movie passes.
A) 1; 3
B) 3; 1
C) 8; 1
D) 1; 4