Please help? A, B, C?

The text is too small to read. Can you you type it out?

first differences:   dı {n} = 1, 4, 7, 12, 13, . . .  (hard to read)

(a)   f{1} = 4  (first term is 4)

   f{n} = 4, 4+1, 4+1+4, 4+1+4+7, 4+1+4+7+12, 4+1+4+7+12+13, . . .
   f{n} = 4, 5, 9, 16, 28, 41, . . .


(b)   Sum [  f{1}, f{2}  ] = 11  (hard to read)   sum of first two terms

and the difference between the first two terms is:  dı {n} = 1

   f{n} = 5, 6, 6+4, 6+4+7, 6+4+7+12, 6+4+7+12+13, . . .
   f{n} = 5, 6, 10, 17, 29, 42, . . .

(c )   f{5} = 27 … (hard to read)

   f{n} = 27-12-7-4-1, 27-12-7-4, 27-12-7, 27-12, 27, . . .
   f{n} = 3, 4, 8, 15, 27, . . .
   f{n} = 3, 4, 8, 15, 27, 27+13, . . .
   f{n} = 3, 4, 8, 15, 27, 40, . . .

a) Start with 4 and add each of the differences in turn.
.. 4, 4+1=5, 5+4=9, 9+7=16, 16+10 = 26, 26+13 = 39
.. The sequence is 4, 5, 9, 16, 26, 39

b) The sum of the first two terms is 11, and their difference is 1. Those terms must be 5 and 6. These are 1 more than the first terms of the sequence in (a). Continue to add 1 for the other terms.
.. The sequence is 5, 6, 10, 17, 27, 40

c) The 5th term of sequece (b) is 27. Sequence c is the same.