< a href =" http : / / www . math . snu . ac . kr / taoffice / calculus / QnA / data / 2019 / L 0442 . 000300 - 2019 - 2 - mid - sol . pdf " target ="_ blank "> http : / / www . math . snu . ac . kr / taoffice / calculus / QnA / data / 2019 / L 0442 . 000300 - 2019 - 2 - mid - sol . pdf </ a >