Very good. but he gave details that must go into account. He gave body weight--125. he is smoking bud so he is probably at least(well go conservative) 15. I would guesstimate that average height for that age is probably 5'5'' giving him around an average metabolism. He hasnt smoked for 3-4 months so his metabolite level would be zero. The size of the blunt is irrelivant because he did not use a specific number it almost insures it wasnt one that would last more than an hour to smoke(like the ounce blunt i rolled over the weekend-hour 26min-) so the saturation of his blood with thc most likely reached the maxamum one time. Myself i would guess he plays a type of school sport and that is why its been 3 or 4 months but there is no evidence to support it but it would also shorten his time testing positive. Given all this information and that most people know the obvious drinking lots of water and urinating as many times as they can before the test, a reasonable person could clearly see that this person should be clear in no more than a few days. Of course everyone reacts differently but collectivly as a species all of us react simillarly in respect to natural human processes such as matabolism, as well as other things like brain activity, and digestion. Its why the term healthy exists. I suppose that like shit when your constipated thc matabolites could stay in the body for an extended and undesired amount of time.