A manufacturer of bicycles builds racing, touring, and mountain models. The bicycles are made of both steel and aluminum. The company has available 57,200 units of steel and 27,600 units of aluminum. The racing, touring, and mountain models need 13, 22, and 26 units of steel, and 9, 21, and 12 units of aluminum, respectively. Complete parts (a) through (d) below. (a) How many of each type of bicycle should be made in order to maximize profit if the company makes $8 per racing bike, $11 per touring bike, and $21 per mountain bike? Let x, be the number of racing bikes, let x₂ be the number touring bikes, and let x3 be the number of mountain bikes. What is the objective function? 2= x₁ + x₂ + x3 (Do not include the $ symbol in your answers.)