v-t graph of two train

The v-t graph of a train travelling between two stations along a straight line.

a. What si the distnace between the stations ?
b. When is the train midway between the stations ?
c. Find the average velocity of the train for this journey ?

My answer
a). 1/2 (20 x 35) + 20 x (100 - 35) + 1/2 (20 x 40)) = 2050 m
b). ??
c). 2050 / 140 = 14.64 m/s

Any comment ?

Tks