4a. [2 marks] A factory produces shirts. The cost. C. in Filian dollars (FJD), o ces shirts. The cost. C, in Fijian dollars (FID), of producing x shirts can be modelled by C(x) = (x - 75)2 + 100. Find the cost of producing 70 shirts. C(70) (70-75) ? +100 (70) = -5?+ 100 C (70). - 12.5.FJD 4b. [2 marks] The cost of production should not exceed 500 FJD. To do this the factory needs to produce at least 55 shirts and at most s shirts. Find the value of s. 4c. [2 marks] Find the number of shirts produced when the cost of production is lowest