A tube with length L connects two reservoirs which contain saltwater. The cross-section in the yz-direction of the tube is so small that we can assume the concentration of the saltwater is the same for any point on a cross-section. Let the concentration of the saltwater in the tube be c(t,x=0)<<L. We assume that the diffusion of the salt is one-dimensional in the tube: ∂c/∂t = D ∂²c/∂x². Determine the boundary and initial conditions according to the following setups: