30. Which one is correct? a. SED + NCRF = 10............ b. SED+NCRF =1............... c. NCRF-SED =1.......... d. 10-NCRF =SED.... 31. A degree of operating leverage of 2.25 means that: a. for every 1% change in operating income there would be a 2.25 change in sales....... b. for every 1% change in sales there would be a 2.25 change in operating income