Suppose that you are designing an experiment for four factors and that due to material properties it is necessary to conduct the experiment in blocks. Material availability restricts you to the use of two blocks; however, each batch of material is only sufficient for six runs. So, the standard 2^4 factorial in two blocks of eight runs each with ABCD confounded will not work. Recommend a design. Suggestion: this is a reasonable application for a D-optimal design. What type of design do you find in each block?