  In this short note, we propose an algorithm based on the expansions of
amplitudes, the dimensional reduction technic and the differential operators,
to calculate the tree level scalar-graviton amplitudes with two massive
scalars, as well as the tree level scalar-photon-graviton amplitudes with two
massive scalars and one photon. While applying the unitarity method, these
amplitudes are necessary inputs for the calculation of post-Newtonian and
post-Minkowskian expansions in general relativity for two massive charged
objects interact with gravity and electromagnetic field.
