Add Random Number in a Column based on defined Number in another Column

I want to add selected numbers in a range (Column C) base on the number defined in column B and have the answer in a different cell. The number in Column B will Change all the time. It could be 1,1,1,3,3,3 or 1,2.3,4,4,5 ect. I am assuming that this is a combination of if, vlookup but really need help


B C
1 25
2 50
3 75
1 100
4 125
5 150

How do you define that 1 return 25 or 100? (based on example)