【大二MATH的几个题请大家帮忙.很着急.mathematicsofinvestment的几个题#1Aperson'ssavingearnaneffectiverateofi=0.12onwhich45%incometaxispaid.Iftheinflationrateis10%peryear,whatistheannualafter--taxrealrateo】

　　大二MATH的几个题请大家帮忙.很着急.

　　mathematicsofinvestment的几个题

　　#1

　　Aperson'ssavingearnaneffectiverateofi=0.12onwhich45%incometaxispaid.Iftheinflationrateis10%peryear,whatistheannualafter--taxrealrateofreturn?

　　#2

　　Acustomerisofferedaninvestmentwhereiscalculatedaccordingtothefollowingforceofinterest:

　　St=0.02to

　　前3题知道怎么做了.......帮我看下第4题吧..

　　#4

　　(a)Ataneffectiveannualinterestrateof12%,calculatethenumberofyears(includingfractions)itwilltakeforaninvestmentof1000toaccumulateto3000.

　　(b)Repeatpart(a)usingassumptionthatforfractionsofayear,simpleinterestisapplied.

　　(c)Repeatpart(a)usinganeffectivemonthlyinterestrateof1%.

　　(d)Supposethataninvestmentof1000accumulatedto3000inexactly10yearsateffectiveannualrateofinteresti.Calculatei.

　　(e)Repeatpart(d)usinganeffectivemonthlyrateofinterestj.Calculatej.