What should come next in the series below?

45G54, 47J57, 50N61, 54S66, ?

Breaking down each term in the series into three components:

45G54: First number = 45, Letter = G, Last number = 54

47J57: First number = 47, Letter = J, Last number = 57

50N61: First number = 50, Letter = N, Last number = 61

54S66: First number = 54, Letter = S, Last number = 66

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Analyzing the first numbers: 45, 47, 50, 54, ?

Differences between consecutive terms:

$47 - 45 = 2$

$50 - 47 = 3$

$54 - 50 = 4$

The differences form the sequence 2, 3, 4, so the next difference is 5.

Next first number: $54 + 5 = 59$

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Analyzing the letters: G, J, N, S, ?

Finding their positions in the alphabet:

G = 7th letter

J = 10th letter

N = 14th letter

S = 19th letter

Differences between positions:

$10 - 7 = 3$

$14 - 10 = 4$

$19 - 14 = 5$

The differences form the sequence 3, 4, 5, so the next difference is 6.

Next position: $19 + 6 = 25$

The 25th letter is Y.

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Analyzing the last numbers: 54, 57, 61, 66, ?

Differences between consecutive terms:

$57 - 54 = 3$

$61 - 57 = 4$

$66 - 61 = 5$

The differences form the sequence 3, 4, 5, so the next difference is 6.

Next last number: $66 + 6 = 72$

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The next term in the series is 59Y72.

Therefore, the answer is Option 3: 59Y72.