A sporting goods store sells tennis rackets that cost $130 for $208 and court shoes that cost $50 for $80.

(A) If the markup policy of the store for items that cost over $10 is linear and is reflected in the pricing of these two items, write an equation that expresses retail price R in terms of cost C. 

(B) What would be the retail price of a pair of in-line skates that cost $120? 

(C) What would be the cost of a pair of cross-country skis that had a retail price of $176? 

(D) What is the slope of the graph of the equation found in part (A)? Interpret the slope relative to the problem.