Write the exponential function $y = 150 e^{-0.13 t}$ in the form $y = ab^t$.

(a) Once you have rewritten the formula, give $b$ accurate to at least four decimal places.
$\ b =$ help (numbers)

If $t$ is measured in years, indicate whether the exponential function is growing or decaying and find the annual growth/decay rate. The rate you determine should be positive in either the case of growth or the case of decay (by choosing decay, the negative rate is implied).

(b) The annual ? growth decay rate is % per year (round to the nearest 0.01%).