need help with question 4. thanks

4. In 1990, the population of Winnemucca, Nevada was 6191 people. The population in Winnemucca, Nevada in 2000 was 9164. (a) (4 points) Write a linear function equation p(t) that represents the population of Winnemucca, Nevada (b) (4 points) When will the population of Winnemucca, Nevada be 3000