A swimming pool can be filled by a hose in 8 hours. It can be emptied by a drainpipe in 12 hours. If the drainpipe is open while the tank is filling, find how long it will take to fill the pool. [Hint: The pool could be
mone-eighth filled in one hour.]

So don't take my word i'm not exactly a mathematical person but i would assume a. because while selling the soap every month you increase in sells so you would by 11 percent. the you would get the factor 0.89 which if i had to guess would be the monthly profit over 11 probably wrong tho