A Drawing Is Placed 40 Cm in Front of a Thin

A drawing is placed 40 cm in front of a thin lens.If a virtual image forms at a distance of 50 cm from the lens,on the same side as the drawing,what is the focal length of the lens?

A) -45 cm
B) 75 cm
C) 90 cm
D) 200 cm
E) +45 cm