I need help with this question please

Total Marginal Average Marginal Output Price Revenue Total Cost Cost $100 $100 $100.00 $30 90 80 63.00 26 80 60 52.67 32 70 40 49.50 40 60 20 49.60 50 50 0 50.00 52 40 -20 52.29 66 30 -40 55.75 80 20 -60 60.67 100 10 -80 67.60 130 Refer to the data for a nondiscriminating monopolist. At its profit-maximizing output, this firm will be operating in the: 1) perfectly elastic portion of its demand curve. 2) perfectly inelastic portion of its demand curve. ( 3) elastic portion of its demand curve. ( 4) inelastic portion of its demand curve