A grocery store finds that the number of boxes of a new cereal sold increases each week. In the 1st week, 26 boxes of the cereal were sold. In the 2nd week, 58 boxes of the cereal were sold and in the 3rd week 90 boxes of the cereal were sold. The number of boxes of cereal sold each week represents an arithmetic sequence. Show all work!
A) State the explicit rule for the arithmetic sequence that defines the number of boxes of cereal sold in week n.

B) Use this rule to calculate how many boxes of cereal will be sold during the 9th week.