Zhang Li, a single white-collar worker, has accumulated a deposit after five years of work. As the amount of the deposit is not enough to buy a house, consider temporarily diversifying it into stocks, gold, funds, treasury bonds and foreign exchange. The investment of the deposit needs to meet the following conditions: (1) if the investment ratio of gold is higher than 1/2, the rest will be invested in treasury bonds and stocks; (2) if the investment ratio of stocks is less than 1/3, then the rest cannot be invested in foreign exchange or treasury bonds; (3) if the proportion of foreign exchange investment is less than 1/4, the rest will be invested in funds or gold; (4) the investment ratio of treasury bonds can not be less than 1/6.
Based on the above information, the proportion of foreign exchange investment is not less than 1/3 can be derived.