4. This morning, you found the following equation in a laboratory book next to a furnace with an Fe-C diffusion couple 10mm thick within it. The book was left by your classmate who had to leave town suddenly. The purpose was to get the tail at least 1mm deep before doing a clever quench experiment. Determine when it is time to quench the specimen, given that it started on 1 January 2023. The furnace temperature is 1100C. \{Note February has 28 days (this year), March, April, June, September and November have 30 days; all the other months have 31 days 1.2%0.4%c(x,t)0.4%=(1/2)[1erf(x/(4Dt))]