#problem-formulation

Question 1: Single choice

A Mars rover must collect one rock of each of 10 types and return to the lander; the path cost is the distance driven (plus a weight penalty that is never negative). Several map squares hold each rock type. With $l$ types already collected, which heuristic is admissible for A*?

The distance from the rover back to the lander1
The sum of the distances from the rover to the $10 - l$ closest squares of missing types2
The length of the shortest tour through the $10 - l$ closest squares of missing types3
The number of missing rock types times the largest distance on the map4

#problem-formulation

Timed test