Pluto's distance $P(t)$ (in billions of kilometers) from the sun as a function of time $t$ (in years) can be modeled by a sinusoidal expression of the form $a\cdot\sin(b\cdot t)+d$.
At year $t=0$, Pluto is at its average distance from the sun, which is $6.9$ billion kilometers. In $66$ years, it is at its closest point to the sun, which is $4.4$ billion kilometers away.
**Find $P(t)$.**
*$\textit{t}$ should be in radians.*
$P(t) = $ [[☃ expression 1]]