Confusion over percentage volume
My assumptions:


'ul' Refers to microlitres, be careful that the addition of B is in millilitres.
You are trying to calculate the % v/v that is being removed from the total solution at the end?


So before incubation the total volume is 2ul + 4ul + 2.2ul + 1.8 ul = 10ul (0.01ml)
You are adding in 0.95ml, totalling 0.96ml.
You are then taking 150ul (0.15ml)
This equates to (0.15/0.96)*100 %
= 15.6%