S = 2.4.6 + 4.6.8 + ... + 98.100.102
=> 8S = 2.4.6.8 + 4.6.8.8 + ... + 98.100.102.8
=> 8S = 2 4 6 (8 - 0) + 4 6 8 (10 - 2) + + 98 100 102 (104 - 96)
=> 8S = 2.4.6.8 - 0 + 4.6.8.10 - 2.4.6.8 + ... + 98.100.102.104 - 96.98.100.102
=> 8S = 98.100.102.104
=> S = 98.100.102.104/8
=> S = 12994800