The bottom of Ignacio's desktop is
74.5

cm
74.5cm74, point, 5, start text, c, m, end text from the floor. Ignacio sits in his adjustable chair, and the tops of his legs are
49.3

cm
49.3cm49, point, 3, start text, c, m, end text from the floor. Each clockwise rotation of the knob on the chair raises Ignacio's legs by
4.8

cm
4.8cm4, point, 8, start text, c, m, end text.

r<5.25

Step-by-step explanation:

Function Modeling

The problem gives us the following conditions: The bottom of Ignacio's desktop is 74.5 cm from the floor, and the top of his legs is 49.3 cm from the floor. We know the chair where he's sitting at has a knob that raises the legs 4.8 cm per clockwise rotation r. This means that the total distance the legs are raised for r rotations is . The total distance of his legs from the floor is then:

49.3+4.8r

This distance cannot reach or exceed 74.5 cm, thus

49.3+4.8r<74.5

Solving for r

Or, equivalently

r<5.25

(a) the volume of the cone is 20/3 in3

hence, option a is correct.