To find the cost per box of donuts, you need to divide the total cost by the number of boxes. In this case, the function C(d) represents the total cost, and the number of boxes is represented by d. Therefore, the cost per box of donuts is given by the equation C(d)/d.
To find the flat rate shipping charge, you can look at the equation of the function C(d). In this case, the flat rate shipping charge is the constant term in the equation, which is 2.
To find the total cost of ordering 3 boxes of donuts, you can substitute d = 3 into the equation C(d) = 8d + 2. So, C(3) = 8 * 3 + 2 = 26. Therefore, the total cost to order 3 boxes of donuts would be 26.