A photographer uses a chemical concentrate to develop film. Initially, 100 mL of concentrate was mixed with water to make 800 mL of developing solution. A new, improved formula allows the same 100 mL of concentrate to make 1200 mL of developing solution. If the photographer needs to prepare 600 mL of developing solution using the new improved formula, how many milliliters of the concentrate should they use?
40
45
50
55
60
