The cost of a computer system increases with increased processor speeds. The cost C of a system as 4) a function of processor speed is estimated as C = 11S2 - 7S+ 1000, where S is the processor speed in MHz. Find the processor speed for which cost is at a minimum. Round to the nearest tenth if necessary. 0.3 MHz B) 2.5 MHz C) 6.4 MHz D) 0.4 MHz​