8. A rectangle is measured to be 6.4 +0.2 cm by 8.3 $0.2 cm. a) Calculate its perimeter in cm
b) Calculate the uncertainty in its perimeter.

Carbon is allowed to diffuse through a steel plate 15 mm thick. the concentrations of carbon at the two faces are 0.65 and 0.30 kg c/m^3 fe, which are maintained constant. if the preexponential and activation energy are 6.2 x 10-7 m2 /s and 80,000 j/mol, respectively, compute the temperature at which the diffusion flux is 1.43 x 10^-9 kg/m^2 -s.