4. Which of the following is true with regards to the concept of a Surplus Variable? it is a variable inserted in a greater-than or equal to constraint to create equality it represents the amount of resource usage above the minimum required usage it is not a part of the LP body of knowledge none of these 3. Which of the following is true with regards to the concept of Integer Linear Program: the parameter values are known with certainty the applicable functions and constraints' returns are constant there is no interaction between decision variables O a model in which some or all of the decision variables are restricted to integer values the results can be shown as fractions none of these