Mixed Integer Optimization

Hello,

I have a simple symbolic optimization model includes integer and real numbers

Minimize[{-ax - bz - ct - f + n, 
  n <= (ax + bz + ct + f) && n >= (ax + bz + ct + f)  && 
   1 <= x <= 105 && 1 <= z <= 30 && 1 <= t <= 22  && 7500 <
    a && a <= b <= c && c <= 2*a && x + z + t <= 22 && 
   x + z + t >= 22 && (ax + bz + ct) h <= f  }, { a, b, c, h, x, t, 
  z , n}]

the answer is

{0, {a -> 7500, b -> 9000, c -> 12000, x -> 3/2, t -> 3/4, z -> 3/4,  n -> f + tc + xa + zb}}

I need to know to define x,z,t as integers, any help is highly appreciated. Given that I am using latest Mathematica version where mixed integer supposed to be supported. wherever I define these variables as integers it will show an error. any idea?

I am not expert, this is my first try with Mathematica.

NMinimize can make some variables integers and some real, but Minimize cannot.

Thank you. Can you please let me know how to define variables within NMinimize

x?Integers can be used to specify that a variable can take on only integer values.

(from the documentation)