Your parents are interested in getting advice on what is the best outcome at the end of a six-year period for investing a sum of money in the following options.

A. Invest $6,000 as a lump sum today.

B. Invest $2,000 at the end of each of the next five years.

C. Invest a lump sum of $2,500 today and $2,000 at the end of the next five years.

D. Invest $1,200 at the end of year one, end of year three and end of year five.

Given an interest rate of 10% per year, what is the preferred option? Justify all relevant calculations.