Dominic sent a chain letter to his friends, asking them to forward the letter to more friends. The relationship between the elapsed time ttt, in hours, since Dominic sent the letter, and the number of people, P_{\text{hour}}(t)P hour (t)P, start subscript, start text, h, o, u, r, end text, end subscript, left parenthesis, t, right parenthesis, who receive the email is modeled by the following function: Phour(t)=18⋅(1.05)t