A person using a magnifying glass as in Figure 26.39b observes that for clear vision its maximum

Question:

A person using a magnifying glass as in Figure 26.39b observes that for clear vision its maximum angular magnification is 1.25 times as large as its minimum angular magnification. Assuming that the person has a near point located 25 cm from her eye, what is the focal length of the magnifying glass?
In figure 26.39