SC-CO2 SC-CHA SC-N,O Emission (2020 $/metric ton of CO,) (2020 $/metric ton of CH.) (2020 $/metric ton of N,0) Year 2.5% 2.0% 1.5% 2.5% 2.0% 1.5% 2.5% 2.0% 1.5% 2020 120 190 340 1,300 1,600 2,300 35,000 54,000 87,000 2030 140 230 380 1,900 2,400 3,200 45,000 66,000 100,000 2040 170 270 430 2,700 3,300 4,200 55,000 79,000 120,000 2050 200 310 480 3,500 4,200 5,300 66,000 93,000 140,000 2060 230 350 530 4,300 5,100 6,300 76,000 110,000 150,000 2070 260 380 570 5,000 5,900 7,200 85,000 120,000 170,000 2080 280 410 600 5,800 6,800 8,200 95,000 130,000 180,000 Source: EPA (2022). Table above shows the social cost of carbon dioxide (SC-CO2), methane (SC-CH4), and nitrogen oxide (SC-N20). a) Explain briefly why the SC-CO2 increases over time. b) Explain briefly the role of discount rate in estimating SC-CO2 and intergenerational climate impact evaluation