4n -12 >n
4n > n + 12
3n > 12
n > 4
So 5,6,7,8,9, and so on
If the top is $48 and it is 60% off you will multiply the cost by the decimal form of the sale percentage: 48*0.60= $28.80. This is the amount she will save and I think is the answer you are looking for.
If there is a follow up question asking for the final cost of the top you would find that by subtracting the amount saved from the original cost: 48.00-28.80=$19.20.
SA=201.7cm^2
I used the equation
SA=pi^1/3(6*V)^2/3 in case you have any more questions like this