Physics Thin Lens Equation Help Please

Question

The actual light sensor size of a digital camera is 14.9 mm X 22.3 mm. You want to take a photograph of your friend, who is 2.0m tall. Your camera has a 50mm-focal-length lens. How far from the camera should your friend stand in order to produce a 22 mm tall image on the light sensor(in meters)?

What I did was convert all the values into meters and plug them in the thin lens equation as follows:

1/do + 1/0.022 = 1/.05

1/do = (1/.05) - (1/.022)

1/do = -25.45

do = 1/ -25.46

do= -0.039 m

I entered -0.039 m and it was wrong. Please help if you can.

Answer 1

k = 2m/0.022m = 1000/11 = d/f; f = 11d/1000;

1/d + 1/f = 1/0.05 = 20;

1/d + 1000/11d = 20; 11 + 1000 = 220d; d = 1011/220 = 4.6 m