Activity A has a duration of 6days and has 4 days of free float. The ES of the successor activity, Activity B, is day 18. If Activity A is delayed by 7 days, What is the adjusted ES of Activity B?

1.25 days
2.21 days
3.31 days
4. 11 days

please help me with the above question. i did not get how to arrive the answer. hoping someone will reply