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 a 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