An aerospace company makes ceramic tiles for shuttle thermal protection systems. As an intermediate stage in the manufacturing process, the company produces large blocks of ceramic. These blocks are initially at a temperature of 900°C, but need to be cooled to 50°C before further processing can take place. The company has two options to achieve this: active or passive convective cooling. Although both methods will achieve the desired results, there are cost and time issues that have to be considered. To make this decision, the company must determine the time required for the core of the block to cool to a temperature of 50°C, given changes in the dimensions of the block and other parameters.