Sum of diagonal entries of MTM is ∑αi2​.∑i=19​ai2​=5PossibilitiesI. 2,1,0,0,0,0,0,0,0, which gives 7!9!​ matricesII. 1,1,1,1,1,0,0,0,0, which gives 4!×5!9!​ matricesTotal matrices =9×8+9×7×2=198