Im quite new to Mathematica and im trying to perform an optimisation of a function using the NMaximise tool. However, I want to place a number of constraints upon the optimisation. Below is my attempt at the optimisation:

NMaximize[{(
  6 (2 ? Rp + 2 (2.6` - c - 2 l Cos[?/2] - 2 Sqrt[Rp^2 - l^2 Sin[?/2]^2])))/
(a k (2 Rp + 2 l Cos[?/2])), (k ((g1 + g2)/2 + 
((-g1 + g2)^2 p)/(2 ?^2 (2.6` - c - 2 l Cos[?/2] - 
          2 Sqrt[Rp^2 - l^2 Sin[?/2]^2])) + (2.6` - c - 2 l Cos[?/2] - 
        2 Sqrt[Rp^2 - l^2 Sin[?/2]^2])/p))/(
    2 ? Rp + 2 (2.6` - c - 2 l Cos[?/2] - 
        2 Sqrt[Rp^2 - l^2 Sin[?/2]^2])) ? 
    Integer && (g1 + g2)/2 + ((-g1 + g2)^2 p)/(2 ?^2 (2.6` - c - 2 l Cos[?/2] - 
        2 Sqrt[Rp^2 - l^2 Sin[?/2]^2])) + (2.6` - c - 2 l Cos[?/2] - 
      2 Sqrt[Rp^2 - l^2 Sin[?/2]^2])/p ? Integer && (
    2 ? Rp + 2 (2.6` - c - 2 l Cos[?/2] - 
        2 Sqrt[Rp^2 - l^2 Sin[?/2]^2]))/k ? Integer}, {Rp, l, ?}]

What I want to achieve is to find the values for Rp, L and Beta so that the function before the comma is maximised. The constraints I wish to place on the system are that each of the functions after the first comma must be whole, positive numbers. I should also mention that a, k and c in the above equation are simply just numbers that I have a value for.

Many thanks for your help.