A project comprises of activities A$,$ B$,$ C$,$ D$,$ E$,$ F$.$ The duration of project is $257$ days. The duration for activity D is $72$ days and it has the slack of $28$ days. Suppose activity D is delayed and no other activity is delayed. As a result of this delay in D$,$ the project duration increased by $23$ days.

What is the delay $($in number of days$)$ in activity D$?$