hi!

So I'm studying for this exam and i came across one exercise in which i must a) calculate the concentration after a period of time b) calculate the time in which concentration fall to random value. i have a plate which is in bowl so only top of the plate is exposed to air..so from the given data there is unsteady translation of the plate with negligible internal resistance on the bottom of the plate so --> m=0 and n=1. i have no problem reading the chart when n<1, but what about in this case? can someone help?

http://www.reviewpe.net/penotes/heat_t/fig_5.09.jpghere is the chart