Lisa Loh is currently working on a retirement plan with her financial planner. It is estimated that Lisa will require $24,000 per annum in retirement income and she expects to spend 30 years in retirement. Assuming an inflation rate of 2% and an average investment return of 4% during her retirement years, what is the estimated lump sum needed at retirement?

$551,077

$548,265

$431,609

$540,483