According to the Jenss model for predicting the height of preschool children, the rate of growth of a typical preschool child is
$$
R(t)=25.8931 e^{-0.993 t}+6.39 \quad\left(\frac{1}{4} \leq t \leq 6\right)
$$
centimeters/year, where $t$ is measured in years. The height of a typical 3 -mo-old preschool child is $60.2952 \mathrm{~cm}$.
a. Find a model for predicting the height of a typical preschool child at age $t$.
b. Use the result of part (a) to estimate the height of a typical 1-yr-old child.