I'm going back over my notes from Japanese For Busy People. I no longer have the books but I wrote out many of the examples. What I have not always done is write down my teacher's explanations. Hopefully I can get an answer here.
In these two examples we see けっこう and いい used. I remember using けっこう for saying one does not want any more tea (いいえ、もう けっこう です) but I don't know if it is the same usage here. More commonly I use もう いい です. So seeing けっこう here has confused me.
Could somebody explain the difference between these two examples please?
今 ペンが ありません。 えんぴつで も いい です か。
はい、えんぴつで も けっこう です。今 現金が ありません。 カードで も いい です か。
はい、 カードで も いい です。