Petroleum has been discovered in the Western region of Uganda after the extraction of petroleum how will the extraction of petroleum contribute to the development of Uganda?

One of the following  refers to the specific  decision  variable value or values  providing the 'best'output
A,  optimal solution
B,    Trial and - error solution
         Given :c(x)=,6000+3x, R(x) = 6(x)
C,    cost and volume models
D,      profit  and  volume  models