Consider the Following Partial Computer Output for a Multiple Regression

Consider the following partial computer output for a multiple regression model.
$$\begin{array}{l}\begin{array} { l l l } \text { Predictor } & \text { Coefficient } \left( \mathrm { b } _ { \mathrm { i } } \right) & \text { Standard Dev } \left( \mathrm { s } _ { \mathrm { b } } \right) \\\text { Constant } & 99.3883 & \\\mathrm { X } 1 & - 0.007207 & 0.0031 \\\mathrm { X } 2 & 0.0011336 & 0.00122 \\\mathrm { X } 3 & 0.9324 & 0.373\end{array}\\\text { Analysis of Variance }\\\begin{array} { l l l } \text { Source } & \text { df } & \text { SS } \\\text { Regression } & 3 & 31.308 \\\text { Error (residual) } & 16 & 9.378\end{array}\end{array}$$
-How many observations were taken?

A) 3
B) 16
C) 19
D) 20
E) 13