a) Write down the third, ninth and the twenty fifth term of the progression.

b) The arithmetic progression above is such that it is increasing and that the third, ninth and the twenty fifth form the first three consecutive terms of a geometric progression. The sum of the seventh and twice the sixth terms of the arithmetic progression is 78. Calculate;

I) the first term and the common difference of the arithmetic progression.

II) the sum of the first nine terms of the arithmetic progression