Julian is using a biking app that compares his position to a simulated biker traveling julian's target speed. when julian is behind the simulated biker, he has a negative position. julian sets the simulated biker to a speed of 20\,\dfrac{\text{km}}{\text{h}}20 h km 20, start fraction, start text, k, m, end text, divided by, start text, h, end text, end fraction. after he rides his bike for 151515 minutes, julian's app reports a position of -2\dfrac{1}{4}\,\text{km}−2 4 1 kmminus, 2, start fraction, 1, divided by, 4, end fraction, start text, k, m, end text. what has julian's average speed been so far?