The expanded sum
7 + 10 + 13 + \dots + 58
is to be rewritten in compact form.
a. (i) Determine how many terms are present in the above sum.
b. (ii) Express the sum in summation notation using an index k that starts from 1.
c. (iii) Using the expression obtained in part (ii), verify that the last term of the series is indeed 58.