Let $P(t)$ be the population of a country, in millions, $t$ years after 1990, with $P(6) = 3.23$ and $P(13) = 3.75$.

(a) Find a formula for $P(t)$ assuming that it is linear.

$P(t) =$ help (formulas)

(b) Find a formula for $P(t)$ assuming that it is exponential.

$P(t) =$ help (formulas)