One measure of student output is the number of completed mat…

One measure of student output is the number of completed math problems produced. Using pen and paper only, a student can complete 50 math problems in 2 hours. Using pen, paper, and calculator, this same student can complete 100 math problems in 2 hours (the calculator had already been invented and the student is already familiar with, and knows how to use the calculator). This scenario best illustrates how the addition of which factor of production can increase output?