Assume c is a char variable. What value does c hold after each of the following state-
ments executes?
$$
\begin{array}{lll} \text { Statement} & \text { Contents of c } \\
\text { c = toupper('a'); } & \_\_\_\_\_\_ \\
\text { c = toupper('B'); } & \_\_\_\_\_\_ \\
\text { c = tolower('D'); } & \_\_\_\_\_\_ \\
\text { c = toupper('e'); } & \_\_\_\_\_\_
\end{array}
$$