Let $a_1,$ $a_2,$ $\dots,$ $a_n$ be real numbers such that \[a_1^2+2a_2^2+\cdots+na_n^2 = 1.\]Find the maximum value of $(a_1+2a_2+\cdots+na_n)^2.$

Campus rentals rents 2 and 3 bedrooms apartments for $700 ans $900 a month respectively. last month they had six vacant apartments and reported $4600 in lost rent. how many of each type of apartment were vacant?