Part A The focal length of David's lens is 20 cm. If Rebecca stands in front of David at a distance of do and David perceives the position of Rebecca at di, what does do equal if the magnification is -0.45? Express your answer with the appropriate units. Follow the sign convention. HA do= -64.4 cm Submit Previous Answers Request Answer X Incorrect; Try Again; One attempt remaining Part B What does di equal? Express your answer with the appropriate units. Follow the sign convention. HA | ? Value Units Submit Request