The Porter-Duff rule "SrcAtop" states that the resulting color is equal to the source color multiplied by the destination alpha, plus the destination color multiplied by the source alpha. Using this rule, the resulting RGBA values of the combined color would be (0.072, 0.4, 0.12, 0.08). This was calculated by multiplying the source values of Red, Green and Blue (0.1, 0.8, 0.2) respectively with the destination alpha (0.2) and then adding that to the destination values of Red, Green and Blue (0.4, 0.5, 0.3) multiplied by the source alpha (0.4).