It's possible to estimate the percentage of fat in the body by measuring the resistance of the upper leg rather than the upper arm; the calculation is similar. A person's leg measures \(40 \mathrm{~cm}\) between the knee and the hip, with an average leg diameter (ignoring bone and other poorly conducting tissue) of \(12 \mathrm{~cm}\). A potential difference of \(0.75 \mathrm{~V}\) causes a current of \(1.6 \mathrm{~mA}\). What are the fractions of

(a) muscle and

(b) fat in the leg?