Please help!

A flask containing an aquatic plant in water is placed next to a light. A sensor that detects the amount of dissolved oxygen (i.e. the amount of oxygen produced by the plant) is placed in the flask, and the light is set on a timer to run on a 12- hour-light, 12-hour-dark cycle for 48 hours.

(a) Explain how the amount of dissolved oxygen will change in the flask during the 12-hour-light cycle if ONLY photosynthesis is taking place during the daytime (i.e. no respiration). Support your explanation using information about the processes that are occurring in the flask.

(b) Explain how the amount of dissolved oxygen will change in the flask during the 12-hour-dark cycle. You can assume that respiration IS taking place at night. Support your explanation using information about the processes that are occurring in the flask.