Keeping c1 constant at c1=15, the interval for c2 in which the current optimal solution remains optimal is 790c2215 907c2152 152c2907 215c2790 none of the above Keeping c1 constant at c1=15, the interval for the net change in c2, represented by c2, while the current optimal solution remains optimal is 67c292 29c276 92c267 76c229 none of the above