its heat and mass transfer, using the Bi method i believe. please solve this with full detail and nearly for a like

A cylinder of stainless steel must be heated in a furnace before it can be processed into the desired shape. The cylinder dimensions are 6 inches diameter and 10 feet long. It is initially at a uniform temp of 200F and the furnace air temperature is 2300F. It must be heated until the entire cylinder is at least 1500F. The heat transfer coefficient of the circulated air to the cylinder is 18 BTU/hr-ft-F. a) What is the minimum length of time that the cylinder must be heated such that every part of the cylinder has reached a minimum of 1500F? Give the best answer you can obtain with textbook information to two significant digits. Note: If a figure is used to answer the problem, specify which one was used and use a simple qualitative sketch to explain how you obtained any information needed to solve the problem (you don't need to scan the textbook figure). Stainless steel alloy properties: k = 11 BTU/hr-ft-F a = 0.19 ft2/hr Cp = 0.11 BTU/lbm-F p = 520 lbm/ft? b) If a different steel alioy is to be processed in the same way, but the new alloy's thermal conductivity is 4 times larger (Cp and p unchanged), can the problem be solved in the same manner as in part a? If not, briefly explain what equation or figure should be used to obtain the most accurate estimate of the time requirement to achieve a minimum temperature of 1500 F within the cylinder? You do not need to solve this problem quantitatively, just outline the method necessary to determine find the required time