When matter and energy change forms within a closed system, A. the total amount of both matter and energy changes. B. the total amount of matter changes, but the total amount of energy does not. C. the total amount of both matter and energy does not change. D. the total amount of energy changes, but the total amount of matter does not.

i believe the answer is true.

i think its 100.

hope this !

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.