Solve the Problem $C$ Of a System as a Function of Processor Speed Is

Multiple Choice

Solve the problem.
-The cost of a computer system increases with increased processor speeds. The cost $C$ of a system as a function of processor speed is estimated as $C=14 S^{2}-5 S+1800$ , 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.

A) $0.3 \mathrm{MHz}$
B) $0.2 \mathrm{MHz}$
C) $3.6 \mathrm{MHz}$
D) $1.4 \mathrm{MHz}$