15. At time t=0, a bullet is fired vertically upwards with a speed of 98m/s. At time
t=5 seconds a second bullet is fired vertically upwards with the same speed. If the air
resistance is neglected. Which of the following is correct?
a. the two bullets will be at the same height above the ground at t=12.5 sec
b. the two bullets will reach back their starting points at the same point
c. the two bullets will have the same speed at t=20s
d. the two bullets will attain the same maximum height