If ∫15f(x) dx=12\int_{1}^{5} f(x) \, dx = 12∫15f(x)dx=12 and ∫35f(x) dx=4\int_{3}^{5} f(x) \, dx = 4∫35f(x)dx=4, find ∫13f(x) dx\int_{1}^{3} f(x) \, dx∫13f(x)dx.
8
16
3
48