Let total time taken is t sec.then after 15 sec, Deceleration =Gradient of line  ⇒2.5=t−1520−0​ ⇒25​=t−1520​ ⇒5t−75=40 ⇒t=23 secTotal distance cover = area under speed time curve =20×15+21​×(23−15)×20=300+80=380 m