Suppose that stock A shares sell at $75 and stock B shares at $115. A portfolio has 300 shares of stock A and 100 of stock B. What are the weights w and 1 - w of stocks A and B in this portfolio? More generally, if a portfolio has N stocks, if the price per share of the jth stock is P_j, and if the portfolio has n_j shares of stock j, then find a formula for w_j as a function of n_1, ..., n_N and P_1, ..., P_N