79. Xiao Zhao, Xiao Qian, and Xiao Sun are practicing running along the lake. The three start from a point on the lake at the same time, with Xiao Qian and Xiao Sun running in the same direction, while Xiao Zhao runs in the opposite direction. Xiao Zhao meets Xiao Qian for the first time, and then $1 \frac{1}{4}$ minutes later meets Xiao Sun for the first time; after another $3 \frac{3}{4}$ minutes, he meets Xiao Qian for the second time. It is known that the ratio of Xiao Zhao's speed to Xiao Qian's speed is $3: 2$, and the circumference of the lake is 2000 meters. Therefore, the time it takes for Xiao Sun to run one lap around the lake is $\qquad$ minutes.
Reference answer: 25