I have to differentiate this equation for a thermo problem but i have forgotten how to do it.

T(y)=(T_s-T_f)exp[-22,000y(m)]+T_f

Initially i was thinking you treat y(m) as a constant and u end up getting 1 for your final answer, however that clearly does not work. T_s and T_f are both T values, just different. Any help is appreciated.