a) At 10 minutes the line is at y - 1, which means she reached 1 km in 10 minutes.
b) The last 30 minutes would be 30 minutes to 60 minutes.
at 30 minutes she was at 0km at 60 minutes she was at 4 km, so in 30 minutes she traveled 4 km. 30 minutes is a half hour, so multiply distance by 2: 4 x 2 = 8, she was traveling at 8 km per hour.
