12A.2 Comparison of the two slab solutions for short times. What error is made by using Eq. 12.1-8 (based on the semi-infinite slab) instead of Eq. 12.1-31 (based on the slab of finite thickness), when at/b = 0.01 and for a position 0.9 of the way from the midplane to the slab surface? Use the graphically presented solutions for making the comparison. Answer: 4%