scaredone

i am 25 yrs old, 6ft 2in, 180 lbs. i havent smoked bud for like 4-5 months prior to november 23rd. on nov. 22nd 2007 i smoked 4-5 hits of low grade marijuana from a blunt and was pretty damn stoned, the next day, nov 23rd, i smoked about 5 hits from a hitter/bat and was fairly high. today, nov. 24, ive taken about 1000mg of niacin and i plan on doing this and exercising for the remaining days until my drug test/urinalysis for probation(sensitive tests ive heard). im not sure when this will be, but i know it will be probably in about 1 week. i know everybody is different and there is really NO way of knowing, but does anyone have a rough idea of how long it will take to rid my system of all thc metabolites? im confident it will be about 7 days since i am skinny(high metabolic rate), the weed was shitty, and i am a very infrequent smoker. plus i am taking niacin and plan on exercising daily for the next 7+ days. what do you guys think???