The muscles of a runner transform chemical potential energy into

AB = 100 km; BC = 80 km; AC = 180 km

Arrival time = 11:30

Explanation:

1. Distance from A to B

(a) Travel time

Time = 10:00 - 8:00 = 2.00 h

(b) Distance

Distance = speed × time = 50 km/h × 2.00 h = 100 km

2. Distance from B to C

Distance = 80 km/h × 1 h = 80 km

3. Distances

AB = 100 km

BC =    80 km

AC =  180 km

4. Arrival time

Start from A       = 08:00

Travel time to B =   2:00

Arrive at B          =  10:00

Wait time at B    =    0:30

Start from B        =  10:30

Travel time to C  =   1:00

Arrive at C            = 11:30