Explain why, if some investors are subject to systematic behavioral biases while others pick efficient portfolios, the

Question:

Explain why, if some investors are subject to systematic behavioral biases while others pick efficient portfolios, the market will not be efficient?
Portfolio
A portfolio is a grouping of financial assets such as stocks, bonds, commodities, currencies and cash equivalents, as well as their fund counterparts, including mutual, exchange-traded and closed funds. A portfolio can also consist of non-publicly...