A town is organizing a parade. There will be floats of only 2 sizes, 30ft. and 15ft. A space of 10 ft. will be left after each float.

a. the parade must be at least 150 feet long, but less than 200ft long. what is the combinations of large and small floats are possible?
b. Large floats cost $600 to operate. Small floats cost $300 to operate. The town has a budget of $2500 to operate floats. what combinations of large and small floats are possible?
Please help! Thank you