Consider a homogenous good industry with four firms. Total demand is given by D(p)=100-p. The variable (=marginal) cost of each of the firms is c1=20, c2=40, c3=50 and c4=55. Firms compete in prices. Suppose firms 1 and 2 merge into one entity and produce with a marginal cost of k>0. What is the threshold value for k below which the merger increases total welfare? [if applicable, round up to the second decimal place.]