3.2: wrote sys_nice, passes tests but incoherence exists between tests and wording

kernel/sysproc.c

@@ -75,7 +75,15 @@ sys_sleep(void)
 
 uint64
 sys_nice(void){
-  return 0;
+  int pid, priority;
+
+  if(argint(0, &pid) < 0 || 
+    argint(1, &priority) < 0 || 
+    priority < 0 || 
+    priority >= NPRIO)
+    return -1; // if an argument is obviously wrong, return -1
+  
+  return nice(pid, priority);
 }
 
 uint64