6. An arithmetic series has sixth term 28 and tenth term 44.

a) Find the first term and the common difference.

U6 = a + (6-1)d, 28 = a +5d---(1)

U10 = a + (10-1)d, 44 = a + 9d---(2)

(1) - (2)

16 = 4d

d = 4

a = 15 - 5 * 4

a = 8

b.Find the sum of the first terms of the series.

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