2-34 Fast Food Fantasy (Triple-F) cooks differ- ent types of hamburgers j = 1,...,4 in batches. A batch of burger j consists of at most u; units and requires the entire cooking grill for t; minutes. Assuming that the hourly demand for each burger is a known quantity d;, Triple-F would like to decide the best batch size for each product. All required batches (and fractions of batches) must fit within the available grill time e sh hour, and the time re- quired to sell out each burger should be minimized so that none will get too cold waiting to be sold. (a) Explain why appropriate decision variables for a mathematical programming model of this problem are (j = 1,...,4) x; 4 batch size of burger j (b) Formulate a system of 4 objective functions, minimizing the time to sell out batches of each burger assuming that demand is smooth over time. (c) Formulate a single constraint assuring that all batches needed to meet demand each hour can be cooked. (d) Complete your model with a suitable system of upper-bound and variable-type constraints. (e) Is your model best classified as an LP, an NLP, an ILP, or an INLP, and is it single-or multiobjective? Explain