Final answer:
The cost to the male, in units of direct fitness, for his alarm-calling altruism is 4 units of direct fitness.
Step-by-step explanation:
The cost to the male, in units of direct fitness, for his alarm-calling altruism is 4 units of direct fitness. By giving alarm calls, the male was able to save the lives of two sisters and three offspring, but he was eventually killed by a hawk and as a result, he was not able to produce three surviving offspring that he would have had otherwise. This reduction in his own reproductive success is the cost of his altruistic behavior.