Arthur buys $2,000 worth of stock. Six months later, the value of the stock has risen to $2,200 and Arthur buys another $1,000 worth of stock. After another eight moneth, Arthur's holdings are worth $2,700 and he sells off $800 of them. Ten months later, Arthur finds that his stock has a value of $2,100.

a) compute the annual time-weighted yield rate of the stock over the two-year period.

b) compute the annual dollar-weighted yield for Arthur over the two-year peroid.