When you combine several investments (like shares in different companies) in a portfolio, the portfolio expected return is a weighted average of the expected returns of the individual investments. How do you compute the weights?

		Each investments weight is its market value divided by the market value of the entire portfolio.
		Each investments weight is one divided by the number of investments in the portfolio.
		Each investments weight is the original cost of that investment divided by the total original investment in the portfolio.
		Each investments weight is the number of shares held divided by the total number of shares in the portfolio.