Conduction through hollow, radial one dimensional heat transfer is expressed as
(a) Q = \(\cfrac{2\pi L(t_1-t_2)k}{log_er_2/r_1}\)
(b) Q = \(\cfrac{2\pi L(t_1-t_2)}{k(r_2/r_1)}\)
(c) Q = \(\cfrac{2\pi Llog_e(t_1/t_2)}{(r_2/r_1)k}\)
(d) Q = \(\cfrac{2\pi L(t_1-t_2)k}{log_er_2/r_1}\)