You would like to have $2,500 in 4 years for a special vacation following graduation by making deposits at the end of every six months in an annuity that pays 3.5% compounded semiannually.

1. in order to have $2,500 in 4 years, you should $ at the end of every six months.
2. b.
how much of the $2,500 comes from deposits and how much comes from interest?

Set $r$ is a set of rectangles such that (1) only the grid points shown here are used as vertices, (2) all sides are vertical or horizontal and (3) no two rectangles in the set are congruent. if $r$ contains the maximum possible number of rectangles given these conditions, what fraction of the rectangles in set $r$ are squares? express your answer as a common fraction.