A car has 400 kgm/s worth of momentum and runs into a truck initially at rest. After the collision, the truck has 500 kgm/s worth of momentum. What must be the final momentum of the car and truck combined? A. 500 kgm/s
B. 100 kgm/s
C. 400 kgm/s
D. -100 kgm/s

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.