How would I calculate the total Average SI for 2023? based on given data

How do I calculate the value of the yearly average forecasted demand in Cell I50

C D Time period Average SI Deseasonalized CLICK CELL J2 as output cell for regression Re Month Demand Yearly average Seasonal Index 0.718 3051.21 Mu 0.7950 1/1/19 2192 0.811 2920.66 R S 2/1/19 2369 0.8592 0.8929 0.827 2977.95 Adj 3/1/19 2462 1.0047 0.927 2987.46 Sta 4/1/19 2770 Obs 1.1900 1.086 3021.64 5/1/19 3281 1.1294 1.075 2897.52 6/1/19 3114 0.3398 0.636 1473.63 AN 7/1/19 937 0.8396 0.882 2624.53 8/1/19 2315 2968.86 9/4/19 2814 1.0206 0.948 10/1/19 3318 1.2034 1.197 2770.93 1.258 2568.08 11/1/19 3230 Put yearly average in below cell 1.1715 4284 2757 1.5538 1.635 2620.10 12/1/19 0.7257 3104.10 1/1/20 2230 0.718 2/1/20 2394 0.7791 0.811 2951.48 Inte 3/1/20 2441 0.7944 0.827 2952.55 X V 4/1/20 2701 0.8790 0.927 2913.05 5/1/20 3338 1.0863 1.086 3074.13 6/1/20 3232 1.0518 1.075 3007.31 7/1/20 2351 0.7651 0.636 3697.44 8/1/20 2806 0.9131 0.882 3181.18 9/1/20 2814 0.9157 0.948 2968.86 10/1/20 3592 1.1689 1.197 2999.75 11/1/20 4112 Put yearly average in below cell 1.3381 1.258 3269.33 12/1/20 4864 1.5829 1.635 2974.83 1/1/2 2355 0.634 0.718 3278.10 2/1/21 2951 0.795 0.811 3638.18 3/1/21 2943 0.7929 0.827 3559.75 4/1/21 3333 0.8980 0.927 3594.66 5/1/21 3642 0.9813 1.086 3354.10 6/1/21 3871 1.075 3601.89 7/1/21 2979 0.8026 0.636 8/1/21 3316 1685.10 0.8934 9/1/21 0.882 3367 3759.37 0.9072 10/1/21 0.948 4528 3552.29 1.2200 11/1/21 1.197 4690 Put yearly average in below cell 3781.43 12/1/21 1.2636 6564 1.258 3728.88 3712 1.7685 1.635 4014.56 Use the average seasonal Index 6 Deseasonalized forecast Seasonalized forecast Highest yearly average 3856.31679 2770.396052 Wh 3712 year 2021 3892.810176 3157.533927 3929.303563 3248.522951 Total 3 year demand Total 3 year 42 deseasonalized demand 114500 40 114524.90 3965.796949 41 4002.290335 3677.118041 1345.828948 average 3 year demand Average 3 year 3180.556 deseasonalized demand 3181.247 4038.783721 4075.277107 4340.535943 4111.770493 2591.244887 4148.263879 3626.839641 4184.757265 3931.883989 4221.250651 5010.962061 Highest Average SI 4257.744038 5309.273101 1.64 9 Put yearly average in cell 6961.620786 50 3819.103595