AMPL/MathProg constraints for the "loose cash" puzzle

Question

I try to formulate H.E. Dudeney's "loose cash" problem in AMPL/MathProg code.

Challenge the "loose cash" problem:

What is the largest sum of money-all in current coins and no silver dollars-that I could have in my pocket without being able to give change for a dollar, half dollar, quarter, dime, or nickel?

Problem my approach is incomplete:

set Coins;
param value{t in Coins};
var number{t in Coins}, integer, >=0;
subject to ...
maximize money_value: sum{t in Coins} number[t] * value[t];

data;    
param:  Coins:    value :=
        penny     1
        nickel    5
        dime      10
        quarter   25
        half      50;
end;

Question: How do I formulate the constraints section ... properly?