I've calculated that it will be 704 calculators. I don't know whether your formula is correct, but instead of t, for the first time, I used 4(that represents end of the 4th week) and I got approx. 1039. For the second time, instead of t I used 2 weeks, because the end of second week is the beginning of the third week and I got 335. And, then, from the fourth week result I subtracted second week's result and I got 704. Since the result is approximate I am not sure if it's correct.Will the be any more else solutions?