An investment firm charges commissions on stock trades according to the following commission schedule:

Transaction Size
Commission
$[math] $[math]
$[math] of principal
$[math]$[math]
$[math] of principal
$[math] $[math]
$[math] of principal

Suppose an investor purchases [math] stocks at [math] per share, holds for [math] weeks and then sells the stocks for $ [math] per share. Find the annual simple interest rate earned by this investment.

[math]

(Note: Your answer should be correct to two decimal places to be counted as correct.)