Shortage: $6,000 - 3,598.07 = $2,401.93 needs to be saved.
Your query is really incomplete, because there is no mention when those missing funds will be set aside and how much interest they earn on it.
PV=(FV)/(1+r)^n
FV=6000
r=.06
n=4
So you have;
PV = 6000/(1.06^4)
=6000/1.26247696
PV=4752.652
Subtract what you've already saved from the necessary PV to determine how much more you need. So
4752.562
-2850.000
And you get something like
1902.562
I'm not sure what the rest of your question means. But this is how you would find out the first part, and if there's more to it any time value of money problems can be found out using that formula unless they have a payment stream(that one does not, and you would know if it did).
You in have saved $2,850 in your savings account over the past 2 years. You have just taken it from the savings and invested the entire amount in an investment tool providing a 6% annual return. You want to take a trip to Disney World in 4 years that you estimate will cost $6,000. If you use the entire amount of your investment available in 4 years, calculate as of the beginning of your investment how much more will you need to save for your trip?
Period 4% 6% 8%
1 1.04000 1.060000 1.08000
2 1.08160 1.12360 1.16640
3 1.12486 1.19102 1.25971
4 1.16986 1.26248 1.36049
5 1.21665 1.33823 1.46933
