Thallium-201 is a radioactive isotope that undergoes first-order decay. When the concentration of 201Tl is 0.0042 M, its half-life is 73.0 hours. What is the half-life of 201Tl when its concentration is 0.0136 M?(A) 51.0 hours(B) 73.0 hours(C) 123 hours(D) 236 hours