set TASKS;
set PROCS;

param cost {TASKS};
param dist {PROCS};

var x {i in PROCS, j in TASKS}, binary;

minimize obj: sum{i in PROCS, j in TASKS} x[i,j]*dist[i]*cost[j];

subject to every_task:
  for {j in TASKS}: sum{i in PROCS} x[i,j] = 1;
subject to only_one:
  for {i in PROCS}: sum{j in TASKS} x[i,j] <= 1;

data;
...