In each of the following cases, determine whether a dummy source or a dummy destination must be added to balance the model

a) Supply: a₁=10, a₂ = 5, a₃ = 4, a₄ = 6

Demand: b₁ = 10, b₂ =5, b₃ = 7, b₄ = 9

b) Supply: a₁ = 30, a₂ = 44

Demand: b₁ = 25, b₂ = 30, b₃=10