AMC 12A 2011 Problem 5

Last summer 30 \% of the birds living on Town Lake were geese, 25 \% were swans, 10 \% were herons, and 35 \% were ducks. What percent of the birds that were not swans were geese?

Answer Choices
A. 20
B. 30
C. 40
D. 50
E. 60