Jane bought some markers and pens from a bookstore. Each marker costs $1 while each pen costs $2. If Jane spent a total of $20 and bought 2 times as many pens as markers, find the number of markers bought by Jane.

Johan runs at the rate of 150 m/min and walks at the rate of 50 m/min. He takes a total of 10 min to travel 600 m through running and walking. Find the amount of time Johan spends on running.