Describe how to prepare 10. ml of a 5, 10, 15, and 20 um cv sokution using a 25 um cv stock solution

The equation for dilutions is (concentration1)(volume1)= (concentration2)(volume 2)  
For each of these, concentration 1 = 25 uM, volume 2 = 10 ml, contentration 3 is those listed. Volume 1 will be the amount of the original stock solution needed. The rest of the 10 ml will be made up with water.  
5 uM= (25 uM) (V1)= (10)(5) --> v1= 50/25 = 2 
V1 = 2 ml stock solution + (10-2)= 8ml water 
10 uM = (25 uM)(V1)= (10)(10) 
= 4 ml stock solution + 6 ml water 
15 uM = (25)(V1) = (15)(10) 
= 6 ml stock solution + 4 ml water 
20 uM = (25)(V1)=(20)(10) 
= 8 ml stock solution + 2 ml water