Modern asset allocation is based upon the model developed by Harry Markowitz. Which of the following statements is/are correctly identified with the model?1. The risk, return and covariance of assets are important input variables in creating portfolios.2. Negatively correlated assets are necessary to reduce the risk or portfolios.3. In creating a portfolio, diversifying across asset types (e.g., stocks and bonds) is less effective than diversifying within an asset type.4. The efficient frontier is relatively insensitive to the input variable.