Two streams merge to form a river. One stream has a width of 8.5 m, depth of 3.1 m, and current speed of 2.0 m/s. The other stream is 7.5 m wide and 3.2 m deep, and flows at 2.4 m/s. If the river has width 10.4 m and current speed is 3 m/s, what is its depth?