If people have no ability whatsoever to respond to God,
		
		
	 
According to the way I understand God's word, there is no "inability" to respond to Him...
It's a total lack of 
desire to respond 
in anything other than a negative way, at the "heart" level.
In other words, we as men are predisposed to hating God and His Son, and we will not come to Him lest our deeds should be reproved ( John 3:19-20 ).
If God desires to save someone,
 He has to do the work...or no one comes to Him 
at all.
	
		
	
	
		
		
			how is it then that God found it needful to harden Pharoh's heart
		
		
	 
Because His word 
says that He did, and it also says that He does it to others as well.
Please see Exodus 4, John 12, Romans 9 and Romans 11.
The reason that the Lord hardened Pharaoh's heart against Him is stated in the text...Exodus 4:21:
So that Pharaoh would refuse to let God's people of Israel go from their bondage of slavery in Egypt...
and the Lord God would then respond to that refusal with a series of plagues.
My friend, I've observed over the years that the fact that this event happened the way that it did, seems hard for most professing Christians to believe.
They don't understand why it had to happen, neither do many accept that 
God did the hardening, even though our hearts are already sufficiently hardened ( in our desires and affections ), towards Him and His ways.
Nevertheless, He pointedly says in Romans 9 that He will have mercy on whom 
He will have mercy, and He will harden whom 
He will harden.
May God bless you.