The president of a small manufacturing firm is concerned about the continual increase in manufacturing costs over the past several yearsThe table below series of the cost per unit for the firm's leading product over the past eight years Click on the datafile logo to reference the data $.$ DATA file Year Cost$/$Unit $()$ Year Cost $/$Unit $()21\mathrm{.}20526\mathrm{.}8025\mathrm{.}9031\mathrm{.}00327\mathrm{.}10731\mathrm{.}9025\mathrm{.}9035\mathrm{.}20($a$)$ Choose the correct time