a) total time taken for journey
b) the acceleration during the first part of the journey

Explanation:
a. the total time taken for the journey is 50sec.
b. u=0, v=10m/sec, t=20sec.
a=(v-u)/t = (10-0)/20 = 10/20 = 0.5 m/s².
hope this helps you to solve the problem.