The temperature gradient in a rod 0.5 m long is 80 c/m . The temperature of the hot end of the rod is $\;30^{0}C\;$. Then the temperature of the cooler and is

Question

$(a)\;40^{0}C\qquad(b)\;10^{0}C\qquad(c)\;-10^{0}C\qquad(d)\;15^{0}C$