(a)

The percent of pollution  removed is .

where  : Feet of length of a particular scrubber.

Graph :

Graph the percent of pollution removed as a function of scrubber length.

Note : Length of scrubber is always positive.

 (b)

As the length of scrubber tends infinity the pollution function approaches to .

Observe the graph horizontal asymtote exist at , it means that the function approaches to but not .

Maximum pollution that can be removed by the scrubber is .

Maximum percent of pollution that can be removed by the scrubber is .

(c)

Find maximum length of scrubber that a factory choose to use.

Maximum pollution that can be removed by the scrubber is .

Substitute in .

Apply logarithm on each side.

Apply power property of logarithm  .

Apply property of logarithm .

Maximum length of scrubber that a factory choose to use is feet.

Maximum length of scrubber that a factory choose to use is feet.