4) A crane manufacturer must supply 1200 cranes in July, 1300 in August, and 2000 in September. The monthly costs for producing x>0 cranes is 10x + 350 in July, 15x + 250 in August, and 12x + 150 in September. Cranes made during a month can be used to meet demand for that month or for any future months. The cost of holding a crane for one month is $4, and we have warehouse space for holding up to 300 cranes at the end of any month. Assume that each months production must be a multiple of 100 and use dynamic programming to find the cost minimizing production schedule.