The output of an economic system q, subject to two inputs, such as labor l and capital k, is often modeled by the cobb-douglas production function q=cl^a k^b. when a+b=1, the case is called constant returns to scale. suppose q=12,200, a = 1/6, b= 5/6, and c=42. find the rate of change of capital with respect to labor, dk/dl.