A certain shade of grey paint is obtained by mixing 3 parts of white paint with 5 parts of black paint. If 2 gallons of the mixture is needed and the individual colors can be purchased only in one gallon or half -gallon cans, what is the least amount of paint ,in gallons, that must be purchased in order to measure out the portions needed for the mixture?
A. 2
B. 2 1/2
C. 3
D. 3 1/2
E. 4
A. 2
B. 2 1/2
C. 3
D. 3 1/2
E. 4