Answer:
15
Step-by-step explanation:
This is simply just 5 x 3 = 15
Remember that c is the initial height. Since we the rocket is in a 99-foot cliff, c=99. Also, we know that the velocity of the rocket is 122 ft/s; therefore v=122
Lets replace the values into the the vertical motion formula to get:

Notice that the rocket hits the ground at the bottom of the cliff, which means that the final height is 99-foot bellow its original position; therefore, our final height will be h=-99
Lets replace this into our equation to get:


Now we can apply the quadratic formula

where a=-16, b=122, and c=198


or


or


or

Since the time can't be negative, we can conclude that the rocket hits the ground after 9 seconds.
Since he sold it for $75 more,
% Mark Up = Mark Up/ Cost Price * 100%
% Mark Up = 75 / 125 * 100%
= 0.6 * 100% = 60%
Percent Mark Up = 60%.
Hope this explains it.