(a) Express the circumference of a circle of radius \(R=27.3 \mathrm{~mm}\) with the correct number of significant digits. (b) Let \(a=12.3, b=3.241\), and \(c=55.74\). Compute \(a+b+c\). (c) Let \(m=4.00, n=3.00\), and \(k=7\) (exact). Compute \(f=m^{2} / k\), \(g=n^{2} / k\), and \(f+g\).