Under which of the following conditions is it most beneficial to use a heuristic approach to solve a problem?
1) when the problem can be solved in a reasonable time and an approximate solution is acceptable. 2) when the problem can be solved in a reasonable time that an exact solution is needed. 3) when the problem cannot be solved in a reasonalbe time and an approximate solution is acceptable. 4) when the problem cannot be solved in a reasonable time an exact solution is needed.