Q1- Why is this assignment statement invalid?

$res = "the value is ".$x + $y." pounds";

Q-2 What sequence of characters will be displayed on the user's screen as a result of printing each of these strings? Assume that variable $xyz has the value 296.4.

(a) 'I live at 26 Queen\'s Road'

(b) 'My name is John O'Brien'

(c) 'This is a backslash\\'

(d) "I live at 26 Queen\'s Road"

(e) "My name is John O'Brien"

(f) "This is a backslash\\"

(g) "He said \"Hello\" to me"

(h) "the value of the variable is $xyz"

(i) "the value of the variable is $xyzpounds"

(j) "a strange string \t\t \t\tabc\$xyz $xyz here is a backslash\\"