Add utility sink in garage, plumbing from washer inside the house.

[Jose@FL]

Hi everybody! I want to add a utility sink in my garage and I was wondering if it's ok to tap in the washer machine downspout before the P-trap, as shown in the picture "Option A", or do I have to do it as shown in "Option B", or is there another easier way? One caveat is that the floor of the garage drops down about 4 inches plus the slope, so I basically can't go too high where I tap in because then the sink will be too high in the garage wall. Thanks.