A dry food product has been exposed to a 30% relative-humidity environment

at 15°C for 5 h without a weight change. The moisture content has been measured and is at 7.5% (wet basis). The product is moved to a 50% relative-humidity environment, and a weight increase of 0.1 kg/kg product occurs before equilibrium is achieved.

a. Determine the water activity of the product in the first and second environments.

b. Compute the moisture contents of the product on a dry basis in both environments.