Conditional matrix arrangement in output

Hello every one my problem is in output.

z=[6

21

36]

but ı want to z as

z=[4

21

12]

how can ı fix this problem.Thanks for your answer and the file Untitled2.m uploaded.

Answer 1

[KSSV]

x=[1 2 3 4 5
    6 7 8 9 10
    11 12 13 14 15];

a=1;
b=2;
c=3;
z = zeros(3,1) ; 

idx = x(:,1)<3 ; 
z(idx) = x(idx,2)*b ; 

idx =  x(:,1) >= 3 & x(:,1) < 7 ; %  3<= x(:,1)<7
z(idx) = x(idx,2)*c ;

idx = x(:,1) > 7 ; 
z(idx) = x(idx,2)*a ;