God is good and trustworthy to his people

Exodus 11:1-10
The Plague on the firstborn. the Lord had said to Moses, "I will bring one more plague on Pharaoh and on Egypt. After that, he will let you go from here, and when he does, he will drive you out completely. Tell the people that men and women alike are to ask their neighbors fro articles of silver and gold."
About midnight I will go throughout Egypt. Every firstborn son in Egypt will die, from the firstborn son of Pharaoh, who sits on the throne, to the firstborn son of the slave girl, who is at her hand mill, and all the firstborn cattle as well.
Preliminaries are over: God's warning is about to be realized. This is the end of the road for Pharaoh and his people. But for Israel it is the beginning. This is a day to remember down the ages; when God dealt death to the firstborn sons of Egypt, but spared and freed his own people.
Was it literally 'all' the firstborn, or the best of the young, including Pharaoh's own son? Was the bubonic plague(鼠疫) or poliomyelitis(脊髓灰質炎) God's instruments? We don not know. But the Egyptian were devastated.
Why?
Pharaoh's heart was hardened so he won't listen the last warning plague of the firstborn.
God bring his people not only freedom but also prosperity.
How?
God is good and God is trustworthy to his people.