4. A bicycle manufacturer makes Racing bikes and City bikes. The total monthly production cannot exceed 400 bikes. A Racing bike needs 2 hours of shop work, while a City bike needs one hour. The company has at most 600 hours of shop time available each month. (a) Graph feasible region; (b) Assume that the company makes a profit of $300 per Racing bike, and $100 per City bike. What is the maximum monthly profit and at how many bikes of each kind