[?] Use the command Simplify, Normal etc. to the function inside?

Questions
1

Consider the following code:

{{c20 -> Function[{u}, 
        2^-Pe (2^Pe cinf - B1[1] Gamma[-(Pe/2), u/4])]}}

I want to apply the command Simplify, Normal etc. to the function inside,

2^-Pe (2^Pe cinf - B1[1] Gamma[-(Pe/2), u/4])

Please tell me the way.
Thanks.

2

Here is one way:

{{c20 -> Function[{u}, 
     2^-Pe (2^Pe cinf - B1[1] Gamma[-(Pe/2), u/4])]}};
myFunction = c20 /. %[[1]];
Simplify[myFunction[u]]
3

You could try using Activate/Inactivate. For instance:

Activate @ Simplify @ Inactivate[
	{{c20->Function[{u},2^-Pe (2^Pe cinf-B1[1] Gamma[-(Pe/2),u/4])]}},
	Function
]

(* {{c20 -> Function[{u}, cinf - 2^-Pe B1[1] Gamma[-(Pe/2), u/4]]}} *)