5. A particle P travels in a straight line through a fixed point 0. Its distance s metres,
from O is given by s = t - 98 + 15t + 40, where t is the time in seconds after
motion has begun. Calculate
(a) the distances of P from 0 when its velocity is instantaneously zero,
(b) the values of t when the acceleration has a magnitude of 9 ms ?,
(c) the average speed of P during the first two seconds,
(d) the total distance travelled in the first six seconds.

guys! help me with part (d) please!
answers for part (a), (b) and (c) are: 15 and 47, 4.5, 26 respectively.​