 Solution

Assume that each target's incorporated flux is proportional to its applied power over this operating range, and that the same composition convention is used throughout. The calibration gives $F_A/F_B=0.35/0.65$ at equal powers. Holding the A target unchanged while making the two incorporated fluxes equal therefore requiresThe B power decreases because B originally supplies more material. This linear magnetron sputtering approximation neglects power-dependent yield, target condition, resputtering and changes in sticking probability. A second composition measurement is the experimental check.