Helen plans to invest some money so that she has $$3,900$ at the end of three years. Determine how much should she invest today given the following choices: $($Round intermediate calculations to $6$ decimal places, e$.$g$.2\mathrm{.}512512$ and round final answer to $2$ decimal places, e$.$g$.2,515\mathrm{.}25.)$

a$.4\mathrm{.}38$ percent compounded daily.

Amount required to be invested $

b$.4\mathrm{.}92$ percent compounded monthly.

Amount required to be invested

$