  A two-parameter singularly perturbed problem with discontinuous source and
convection coefficient is considered in one dimension. Both convection
coefficient and source term are discontinuous at a point in the domain. The
presence of perturbation parameters results in boundary layers at the
boundaries. Also, an interior layer occurs due to the discontinuity of data at
an interior point. An upwind scheme on an appropriately defined
Shishkin-Bakhvalov mesh is used to resolve the boundary layers and interior
layers. A three-point formula is used at the point of discontinuity. The
proposed method has first-order parameter uniform convergence. Theoretical
error estimates derived are verified using the numerical method on some test
problems. Numerical results authenticate the claims made. The use of the
Shiskin-Bakhvalov mesh helps achieve the first-order convergence, unlike the
Shishkin mesh, where the order of convergence deteriorates due to a logarithmic
term.
