A culture of bacteria has an initial population of 860 bacteria and doubles every 9 hours. Using the formula P_t = P_0\cdot 2^{\frac{t}{d}}P t ​ =P 0 ​ ⋅2 d t ​ , where P_tP t ​ is the population after hours, P_0P 0 ​ is the initial population, is the time in hours and is the doubling time, what is the population of bacteria in the culture after 4 hours, ?