Energy and respiration: describe question

A student used a simple respirometer to investigate the respiratory quotient (RQ) of germinating mung bean seeds. The respirometer consisted of a sealed tube containing the seeds, with a capillary tube attached to measure gas volume changes. A soda lime pellet was placed in the tube to absorb carbon dioxide. The student recorded the following data over a 30-minute period:

• Volume of oxygen consumed: 2.5 cm³
• Volume of carbon dioxide produced: 2.0 cm³ (measured in a separate setup without soda lime)

Using this data, describe how the RQ is calculated and what the calculated RQ indicates about the respiratory substrate being used by the seeds. In your answer, also explain the role of soda lime and why a control tube is necessary.