Exactly 18 months ago management in a certain retail electronics store began making monthly observations of the percentage of shoppers who appear to be showrooming—examining a product while in the store and then buying the product online from another store. The results of the observations were that the percentage of customers who appeared to be showrooming increased by 0.5% each month. If p is the percent of customers who appeared to be showrooming in their store x months after the monthly observations began and 10 months ago p was equal to 10.5%, which of the following equations most accurately models the findings of the management team for the past 18 months?

A.​ p = 0.5x​

B.​ p = 0.5x + 5.5​

C. ​p = 0.5x + 6.5​

D.​ p = 0.5x + 10.5​

E. ​p = 0.5x + 18