Homework Help: Combination Lens problem

1. Feb 3, 2010

A converging lens of focal length 7.94 cm is 19.7 cm to the left of a diverging lens of focal -6.04 cm. A coin is placed 12.2 cm to the left of the converging lens. A) Calculate the location of the coins final image.

B)Calculate the magnification of the coin's final imag.

The equation i think you are supposed to use is 1/do + 1/di= 1/f

What i have so far is that the image distance from the converging lens in 22.74 cm. I then subtracted that number from 19.7 cm and tried to use that as the object distance for the diverging lens. When i did this and solved for the new image distace i got 2.02 cm which was wrong. Please help