been computed and has the value $c_{2}=-7/(2^{6}3^{5})$. The leading contribution to the low energy effective action comprises all terms with the equivalent of two derivatives or four fermions and is determined in terms of the effective coupling. The next-to-leading contribution to the low energy effective action contains all terms with the equivalent of four derivatives or eight fermions. Using the scale invariance and $U(1)_{\cal R}$ symmetry of the model, Dine and Seiberg argued that the four derivative term is one loop exact. In  the vanishing of instanton corrections to the four derivative terms was explicitly verified and a rigorous proof of this non-renormalization theorem has recently been given in . The one loop contribution to the four derivative terms has been considered in . The result for the low energy effective action, up to and including four derivative terms, in ${\cal N}=2$ superspace, is given by

where $A$ is an ${\cal N}=2$ Abelian chiral superfield. The number of terms that contribute to the low energy effective action at each order, for six derivative terms or higher, increases rapidly and a direct approach to these terms is not feasible. An elegant approach to study these terms has been developed in  for 