We apply Pauli's master equation to spin tunneling in Mn 12 acetate, and argue that the corresponding relaxation is exponential in time. Taking advantage of this simplification we calculate the frequency dependent specific heat. The results are compared with recently obtained experimental ones. We also predict results for experiments in which spin tunneling through lower-energy levels can easily be probed by applying a field transversely to the anisotropy axis. [S0031-9007(98)