How far (in mm) from the lens must the film in a camera be, if the lens has a 40.0 mm focal length and is being used to photograph a flower 61.5 cm away

Can anybody me with this? ? (picture included.)

Which of the following compounds would be primarily ionic? methane, ch4, ammonia nh3, calcium chloride, cacl2, or carbon dioxide, co2

When a pair of 10-n forces act on a box of candy, the net force on the box is a 20 n. b about 14 n. c zero. d any of the above depending on the directions of forces.