Give correct answer with detailed explanation......

1. Give an estimate (rounded to a power of 10) of the number of possible passwords of the following form. In all cases the password length is 10. (a) A password consists of English alphabet in lower case only, e.g. helloworld: (b) A password consists of English alphabet in lowercase and uppercase, e.g. HelloWorld; (c) A password consists of English alphabet in lowercase and uppercase, and digits {0,1,2,3,4,5,6,7,8,9.); e.g. H3110WOrid, 'O' is zero, 'l' is one; (d) A password consists of English alphabet in lowercase and uppercase, digits, and elements of the symbol set {?, !, @, #, $, %, *, (,), -, +}; e.g. H3! !0World. '0' is zero. 'l' is one. (We use "." as a separator for the elements of a set.)