Please Help me!

A 10- year annuity pays $1500 per month, and payments are made at the end of each month. If the interest rate is 15 percent compounded monthly for the first four years, and 12 percent compounded monthly thereafter, what is the present value of the annuity?

I've been thinking for so long, but I still can't find the answer.
So, Can u?

The Present Value of the Annuity is as follows :-

1 1,500.00 1,522.50
2 3,022.50 3,067.84
3 4,567.84 4,636.36
4 6,136.36 6,228.40
5 7,728.40 7,844.33
6 9,344.33 9,484.49
7 10,984.49 11,149.26
8 12,649.26 12,839.00
9 14,339.00 14,554.08
10 16,054.08 16,294.89
11 17,794.89 18,061.82
12 19,561.82 19,855.24
13 21,355.24 21,675.57
14 23,175.57 23,523.21
15 25,023.21 25,398.55
16 26,898.55 27,302.03
17 28,802.03 29,234.06
18 30,734.06 31,195.07
19 32,695.07 33,185.50
20 34,685.50 35,205.78
21 36,705.78 37,256.37
22 38,756.37 39,337.72
23 40,837.72 41,450.28
24 42,950.28 43,594.54
25 45,094.54 45,770.95
26 47,270.95 47,980.02
27 49,480.02 50,222.22
28 51,722.22 52,498.05
29 53,998.05 54,808.02
30 56,308.02 57,152.64
31 58,652.64 59,532.43
32 61,032.43 61,947.92
33 63,447.92 64,399.64
34 65,899.64 66,888.13
35 68,388.13 69,413.95
36 70,913.95 71,977.66
37 73,477.66 74,579.83
38 76,079.83 77,221.03
39 78,721.03 79,901.84
40 81,401.84 82,622.87
41 84,122.87 85,384.71
42 86,884.71 88,187.98
43 89,687.98 91,033.30
44 92,533.30 93,921.30
45 95,421.30 96,852.62
46 98,352.62 99,827.91
47 101,327.91 102,847.83
48 104,347.83 105,913.05

This is where the change takes place.
49 107,413.05 108,702.00
50 110,202.00 111,524.43
51 113,024.43 114,380.72
52 115,880.72 117,271.29
53 118,771.29 120,196.54
54 121,696.54 123,156.90
55 124,656.90 126,152.79
56 127,652.79 129,184.62
57 130,684.62 132,252.83
58 133,752.83 135,357.87
59 136,857.87 138,500.16
60 140,000.16 141,680.16
61 143,180.16 144,898.33
62 146,398.33 148,155.11
63 149,655.11 151,450.97
64 152,950.97 154,786.38
65 156,286.38 158,161.82
66 159,661.82 161,577.76
67 163,077.76 165,034.69
68 166,534.69 168,533.11
69 170,033.11 172,073.50
70 173,573.50 175,656.39
71 177,156.39 179,282.26
72 180,782.26 182,951.65
73 184,451.65 186,665.07
74 188,165.07 190,423.05
75 191,923.05 194,226.13
76 195,726.13 198,074.84
77 199,574.84 201,969.74
78 203,469.74 205,911.38
79 207,411.38 209,900.31
80 211,400.31 213,937.12
81 215,437.12 218,022.36
82 219,522.36 222,156.63
83 223,656.63 226,340.51
84 227,840.51 230,574.60
85 232,074.60 234,859.49
86 236,359.49 239,195.80
87 240,695.80 243,584.15
88 245,084.15 248,025.16
89 249,525.16 252,519.47
90 254,019.47 257,067.70
91 258,567.70 261,670.51
92 263,170.51 266,328.56
93 267,828.56 271,042.50
94 272,542.50 275,813.01
95 277,313.01 280,640.77
96 282,140.77 285,526.46
97 287,026.46 290,470.77
98 291,970.77 295,474.42
99 296,974.42 300,538.12
100 302,038.12 305,662.57
101 307,162.57 310,848.52
102 312,348.52 316,096.71
103 317,596.71 321,407.87
104 322,907.87 326,782.76
105 328,282.76 332,222.16
106 333,722.16 337,726.82
107 339,226.82 343,297.54
108 344,797.54 348,935.11
109 350,435.11 354,640.33
110 356,140.33 360,414.02
111 361,914.02 366,256.99
112 367,756.99 372,170.07
113 373,670.07 378,154.11
114 379,654.11 384,209.96
115 385,709.96 390,338.48
116 391,838.48 396,540.54
117 398,040.54 402,817.03
118 404,317.03 409,168.83
119 410,668.83 415,596.86
120 417,096.86 422,102.02

ANSWER = $422,102.02

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