Answer
$
a-\\
H(10101, 00011)=3\\
b-\\
H(00110, 10111)=2\\
$
Work Step by Step
$H(s, t)
= the\,\,number\,\,of\,\,positions\,\,in\\\,\,which\,\,s\,\,and\,\,t\,\,have\,\,dif\! ferent\,\,values.\\
a-\\
H(10101, 00011)=3\\
10101\\
00011\\
(they\,dif\! fer\,in\,the\,first,third\,and\,forth\,digit)\\
b-\\
H(00110, 10111)=2\\
00110\\
10111\\
(they\,dif\! fer\,in\,the\,first\,and\,fifth\,digit)\\
$