Answer:
Later on, His friend theo informed him about a surprise birthday party for another friend
Step-by-step explanation:
The opportunity cost in the given scenario are the three opportunities that Harry lost.
The opportunity cost is the preference the person had to sacrifice in order to gain other alternatives. It can also be called alternative cost.
In the given scenario, Harry thought of painting his house over the weekend. He also thought of going for fishing. His parents were also insisting him to visit them that weekend. After receiving call from his friend, Theo, he also had an alternative to attend his friend's birthday party.
Out of the four alternatives he had, Harry chose to visit his parents. So, the opportunity cost would be the other three alternatives he had to do at the weekend, i.e. painting his house, going for fishing and friend's birthday party.