4 A contagious and fatal virus has tragically struck the city of Plaguesville, which has been quarantined until the virus has run its course. The function P(t) = 108t - 3t gives the number of people who are newly infected t days after the outbreak began. (a) Find first and second derivatives P'(t) and P"(t). (b) Solve P(t) = 0, P'(t) = 0 and P" (t) = 0. Then complete the table. (c) Use the table to describe the details of the Plaguesville tragedy. (a) Find first and second derivatives P'(t) and P'(t). P'(t) = P''(t) =