A counter-flow heat exchanger cools oil from T_{h,in} = 100^\\circC to T_{h,out} = 60^\\circC using cooling water that enters at T_{c,in} = 20^\\circC and leaves at T_{c,out} = 50^\\circC. The Log Mean Temperature Difference is defined as $\\Delta T_{lm} = \\frac{\\Delta T_1 - \\Delta T_2}{\\ln(\\Delta T_1 / \\Delta T_2)}$, where $\\Delta T_1 = T_{h,in} - T_{c,out}$ and $\\Delta T_2 = T_{h,out} - T_{c,in}$. What is the LMTD for this heat exchanger?