Question 1072367
At t(0) you have 70 lbs of salt in the tank. Since each hour of the process removes 19% of the salt solution, this leaves you with 81% of the salt you had to begin with. So the formula for the process would be:

a)Salt=70 lbs. x .81^t where t is the amount of time, in hours, that the process has been running.

b)To get down to 3 lbs of salt we need:
3=70 x .81^t
.81^t=70/3
t=approximately 14.95 hours

c)$8000/houe x 14.95 hours=  $119584.95

d).1=3 x .81^t
t=16.41
$8000 x 16.41=$131280 to reduce the salt from 3 lbs. to .1 lbs.