Astore bought a chalkboard and marked it up 200% from the original cost of $72. later on, jackie purchased the chalkboard and paid 9.25% sales tax. how much, including tax, did she pay for the chalkboard?

Situation: an archaelogist in turkey discovers a spear head that contains 54% of its original amount of c-14. n = noekt no = inital amount of c-14 (at time t = 0) n = amount of c-14 at time t k = 0.0001 t = time, in years find the age of the spear head to the nearest year