In call by name, parameter is evaluated when it is used, not when the function is called. Hence every time in function P, a,b and c will refer to y,x and x respectively. However x is a local variable of P so x in function P will be value of 3.
In line b = b+x+6, b will refer to global variable x that will be equal to 5+3+6 = 14
In the next line c = c+a, again the value of global variable x will be equal to 14+10 = 24
So, finally value of x has become 24, whereas the value of y remains as it is that is 10.
