A culture of bacteria starts with 1,000 bacteria and grows at a rate propotional to its number. She already has 3,000 bacteria after 4 hours. Find an expression P(t) for the number of bacteria after t hours. Calculate the number of bacteria after 7hours (round the answer to the nearest integrer). What is the population growth rate After 7 hours?(round the answer to nearest integer). How long does it take for membership to rise to 9,000 units?(round the answer to nearest integer).