From the question, we were told that a vacation cruise is going to cost at least $9,000.
We are to find the cost (c) of each if three sisters want to pay equal amount.
First recall that the question said at least $9,000. And at least would mean in this contest that it is either 90 or above.
So, since they are three sisters, then we divide the 9000 by 3.
= 9000/3
= 3000
3000 is the least to pay.
So, introducing the c for the cost, it now means:
c ≥ 3000
Therefore, the correct option is the fourth option which is c ≥ 3000