Starting six months after her grandson​ Robin's birth, Mrs. Devine made deposits of ​$210 into a trust fund every six months until Robin was twenty-one years old. The trust fund provides for equal withdrawals at the end of each six months for three ​years, beginning six months after the last deposit. If interest is 6.9​% compounded semi-annually​, how much will Robin receive every six months​?
Robin will receive ​$_?. ​(Round the final answer to the nearest cent as needed. Round all intermediate values to six decimal places as​ needed.)