$1.(30\%)$ Compute the capacity of the following sets of strings:

$($a$)$ The set of all finite$-$length binary strings containing an even number of $1$s$.$

$($b$)$ The set of all finite$-$length strings over the alphabet Sigma $=\backslash \{0,1,2,3\backslash \}$ such that even positions do not contain any Os$.$