Error while using raster calculator in model builder

I am trying to use the model builder for the RUSLE Model. Well this is how the model looks like:
Attachment 24064

So in the raster calculator I have a formula which also involves the rasters generated in the model. This is error which I get .Could anyone tell me what could be going wrong.
Attachment 24065

Below is the forumla which I am using in the first raster calculator block:

Power( [ "%FlowAcc_Flow%" ] * 10 / 21 , 0.4 ) * Power( Sin( "%Slope_Fill%" ) / 0.09 , 1.4 ) * 1.4

I am just trying to use it in the model and not as a python script.

Regards,
Senthil

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